The Surveyors in the Longest Tunnel of the World

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The surveyors in the longest tunnel of the world

Special Edition English Bild: AlpTransit Gotthard Bild: AG AlpTransit Dear reader,

There are very few moments in life providing us with a reason to be proud for the work that has been accomplished. Participating in the construction of the longest tunnel in the world is certainly one of those reasons. The surveyors are too often perceived as minor actors in the big construction projects. Without them, however, a major work such as the construction of a big tunnel couldn’t be realized. The surveying specialist meets many challenges and resolves numerous problems and we hope that the lecture of this booklet will help you to better understand the nature of those challenges.

IGS is proud to present you the articles written by the actors of the «construction site of the century» and wishes you much pleasure and interest while reading them.

Maurice Barbieri IGS President (Ingénieurs Géomètres Suisses) Editorial

Since the citizens of the canton of Schwyz brought the letter of rights they had obtained from Italy over the Gotthard home in 1240, the pass has again and again been of fateful importance for the Confederation. In the dangerous years of World War II, General Henri Guisan set up our armed forces in such a way that the two historic trans-Alpine railway lines Gotthard und Lötschberg- Simplon would have been interrupted if Hitler and Mussolini had ordered an attack. Even today Switzerland sees itself as an independent country in accordance with Article 2 of its Federal Constitution. But Switzerland is not an island of egoists. Therefore, our country has decided to carry out its enormous «new trans-alpine railway» or NEAT project through the Lötschberg and the Gotthard mountains on its own. Europe and the world, however will obviously benefit more from this double digit billion investment than we ourselves. The achievement, however – the reduction in travelling distance and time between Zurich and Milan from four to two hours and 40 minutes – is predominantly a Swiss one.

Achievements such as these are never in vain: Let us recall in silence those workers who, despite modern safety precautions, this time too, like others more than a century ago, died for the sake of duty. But let us also remember the effort and the ingenuity that went into this venture. It includes the triumph of Swiss geomatics. We recall: When the main breakthrough of the tunnel was accomplished on 15 October 2010, the deviation of the two tunnels was only 8 centimetres laterally and 1 centimetre in height. How did the engineers and surveyors manage to achieve such results? Well, parallel to construction mapping and monitoring tasks, instrumental engineering was also promoted so that the precision requirements could be met. Thus, atmospheric effects that have an influence on measurements had to be minimised or directional transmission achieved via the 800 metre deep vertical shaft of Sedrun.

Also the major transition had to be made from the good old triangulation method to the global satellite navigation system and laser scanning.

Once again, the cadastral survey agency in my department, the DDPS, delivered an outstanding performance that fills me with pride. May this booklet provoke similar feelings in many readers and may it provide valuable services to the specialists as a technical reference, but also bear witness to us all of that what we know, at least since Pestalozzi:

Humans have unlimited capabilities if they really set their minds to something!

Best regards

Federal Councillor Ueli Maurer

1 Contents

Editorial 1

AlpTransit Gotthard

R. Simoni: Gotthard and Ceneri Base Tunnels The New Gotthard Rail Link takes shape 4

U. Weidmann: AlpTransit: A European link through the Swiss Alps 8

H. Ingensand: Modern technologies and concepts solving the geodetic challenges of Alp Transit 12

R. Stengele, I. Schätti-Stählin: Geodetic Basis ans Main Control Surveys in the Gotthard Base Tunnel 15

F. Ebneter: The (surveying) challenges at the beginning of the project, when everything was new and unknown 24

A. Carosio: Surveying the longest railway tunnel of the world – The vision of the constructor’s expert 28

R. Deicke: Gotthard Base Tunnel survey challenge from a contactor’s point of view 33

M. Messing: Navigation of the tunnel-boring machine at Gotthard 36

A. Wiget, U. Marti, A. Schlatter: National Surveying ontributions to the AlpTransit Gotthard Base Tunnel 39

D. Stähli, M. Baumeler, Th. Silbermann: Overview of railway technology in the Gotthard Base Tunnel 46

H. Heister, W. Liebl: Measurement Uncertainty of Gyro-measurements in the Construction Works of the Gotthard Base Tunnel 50

D. Salvini, M. Studer: Automatic Monitoring of large Dams in the Swiss Alps during Construction of the Gotthard Base Tunnel (57 km) 58

U. Bättig, S. Bühler, D. Eberhart, R. Bänziger: Versatile surveying outside the tunnel at Altdorf–Erstfeld, Amsteg and Faido 62

J. Gämperle, M. Furrer: Monitoring Measurements at Portal Erstfeld 66

C. Bernasconi: The role of surveying in the construction of the Ceneri Base Tunnel 69

2 Contents

Th. Heiniger: Geomonitoring at the North Portal of the Ceneri Base Tunnel 74

B. Bürki, S. Guillaume: Astro-geodetic measurements of vertical deflections and azimuths for ALPTRANSIT 77

A. Geiger, A. Schlatter: From potential theory to the subsidences at the Gotthard Pass 84

H.-U. Riesen: Surveying work at the Lötschberg Base Tunnel after the final breakthrough 86

B. Tanner: Railway Infrastructure surveying for the Lötschberg Base Tunnel 90

M. Bertges: Deformation Monitoring - Challenge Accepted 96

R. Probst, D. Fasler Isch: 300 surveyors acknowledge many years of precise work 98

3 AlpTransit Gotthard

freight trains on the new Gotthard route Gotthard and Ceneri Base will increase from around 140 trains today to 220 trains per day. The transfer pol- Tunnels icy brings not only economic but also ecological benefits. The New Gotthard Rail Link AlpTransit Gotthard integrates Switzer- land into the European high-speed net- takes shape work for passenger traffic. The passenger trains of the future will travel the new AlpTransit Gotthard is creating a future-oriented flat rail link through the Alps which route at speeds of up to 250 km per hour. will bring marked improvements to rail travel and transportation systems in the heart The Gotthard and Ceneri base tunnels will of Europe. At the centre of the new rail link is the Gotthard Base Tunnel – at 57 km reduce passenger travelling time between the world's longest, and with a rock overburden of up to 2500 m the world's dee- Zurich and Milan from just under four pest, tunnel. Adjoining it to the south in the Canton of Ticino as continuation and ex- hours today to two hours and forty min- tension is the 15.4-km-long Ceneri Base Tunnel. Together, the tunnels form the new utes. There will also be optimal connec- Gotthard Rail Link: a continuous flat route through the Alps. tions between the Swiss and Italian timetable systems in Zurich and Milan.

ciently. The transport offerings for pas- Gotthard Base Tunnel R. Simoni sengers and freight can be substantially Construction concept and route improved. The 57-km-long Gotthard Base Tunnel For goods traffic, the new route allows consists of two parallel single-track tubes. In several referendums, Swiss voters de- freight trains to be twice as long and The two rail tunnels run about 40 m apart cided clearly in favour of protecting the heavy as today. Transporting the same and are joined at approximately 325-m in- sensitive Alpine regions and a corre- quantity of goods will require fewer lo- tervals by connecting galleries. Situated sponding transport policy: as far as pos- comotives and personnel. Freight trains one third and two thirds of the way sible goods traffic should be transferred with a pulled weight of more than 2000 through the tunnel at Sedrun and Faido from the roads to the railways. The New metric tons can cross Switzerland without are multifunction stations containing Gotthard Rail Link provides the central in- stopping and without mid-train or push- track crossovers, components of the ven- frastructure to implement this transfer ing locomotives. The daily number of tilation systems, and technical areas with policy. In view of their extent and the long planning and construction time, the base tunnels under the Gotthard and Ceneri Gotthard-Basistunnel

Gotthard can be regarded as construction projects Schema Tunnelsystem San Gottardo of the century. Several generations of engineers, planners and surveying specialists, as well as several thousand miners, are contributing to their realisation.

Continuous flat route through the Alps

With the AlpTransit Gotthard, a flat rail link through the Alps is being constructed. The highest point of the railway route, at 550 m above sea level, is no higher than

the city of Berne, The maximum gradual gradient of the flat rail link is 12.5 per thousand on the aboveground sections and 8.0 per thousand in the base tunnels. Since there are also no curves with tight radii, long, heavy trains can travel effi- Fig. 1: The tunnel system of the Gotthard Base Tunnel.

4 AlpTransit Gotthard

Support was provided directly from the tunnel-boring machine by means of systematic anchoring and shotcrete. The machines can also insert steel supports in the form of partial or complete rings. At the rear end of the TBM, the tunnel invert is produced from cast-in-place concrete. The sealing for the tunnel tubes is installed from back-up construction sites. Where large-scale water ingress or corrosive water is encountered, full sealing is implemented. The normal cross-section of the inner vault is not steel-reinforced. It is normally 30 to 35 cm thick. In confined rock conditions, inner linings with a wall thick- ness of up to 120 cm are used. In a subsequent work operation, side benches, ground-water pipelines and cable systems are installed. The completed single-track tubes have a minimum free cross section of 41 m2 (usable diameter 8.4 m).

Fig. 2: To stabilise the rock in the Sedrun section, flexible steel rings were in- Present state of work on the stalled. Gotthard safety and switching systems, as well as the Erstfeld, Amsteg, Faido and Bodio sec- As of mid-October 2010, of the total of two emergency-stop stations, which are tions, open hard-rock tunnel-boring ma- 151.8 km of tunnels, galleries and pas- directly linked by separate access tunnels. chines (TBMs) with cutting diameters of sages of the Gotthard Base Tunnel, only Because of the geology between the between 8.8 and 9.58 m were used. For 2.4 km, or 1.6%, remain to be excavat- north portal at Erstfeld and the south por- geological reasons, the main tubes in the ed. Concrete work is in progress in both tal at Bodio, the route of the Gotthard Sedrun section were excavated by con- tubes. Of the total of 114.6 km of tunnel Base Tunnel forms a large letter S. This al- ventional drilling and blasting. lining work, at the beginning of October, lows the route to pass through the struc- turally most favourable rock formations and avoid even greater depths of overly- ing rock. Further factors affecting the choice of route were the locations of the portals and optimisation of the lengths and positions of the intermediate headings. When deciding where to locate the intermediate headings, the most important criteria were ease of access, risk of avalanches, floods, rock falls and land- slides, as well as ground water.

Constructing five sections simultaneously To optimise construction time and costs, drilling took place simultaneously from the portals at Erstfeld and Bodio, as well as from three intermediate headings at Amsteg, Sedrun and Faido. The intermediate headings simplified construction lo- Fig. 3: World record under the Gotthard: on October 15, 2010, the miners cel- gistics as well as the supply of fresh air. In ebrated the final breakthrough in the east tube of the Gotthard Base Tunnel.

5 AlpTransit Gotthard

104.9 km of the invert (92%) and 67.8 systems in the multifunction stations and crosscut infrastructure systems. Extensive km of the vault (59%) had been concret- lining of the tunnel tubes. In the west tube test runs will subsequently be performed ed. On October 15, 2010, the first final of the Bodio section, installation of the in the section. The main installation of the breakthrough of the Gotthard Base Tun- railway infrastructure has already begun. railway systems in the north will take place nel took place in the east tube between The east tunnel continues to be used to starting in 2013. Commercial operation Sedrun and Faido. In April 2010 the final store supplies for the tunnel construction of the Gotthard Base Tunnel with sched- section of rock in the west tube between sites at Faido. Construction of the south- uled train services is planned to start in Faido and Sedrun is scheduled to be cut. ern aboveground approach section is 2017. At the point of breakthrough, the depth complete. Construction of the new Swiss The permanent railway infrastructure sys- of covering rock is 2500 m. The break- Federal Railways (SFR) operations control tems comprise the concreted track bed, through took place with great accuracy: centre (CEP) is in progress. In the future, the catenaries, the electric power supply, the measured deviations were 8 cm hor- all railway traffic between Arth-Goldau the 16.7 Hz tractive power supply, and izontally and 1 cm vertically. and Chiasso will be controlled from this telecommunications installations for Work in the various construction sections CEP at Polleggio. landline, wireless and safety systems. In is at different stages. In the northern addition, for the duration of the con- aboveground approach section (Altdorf- Installation of railway infrastructure struction, temporary systems are re- Rynächt), work is in progress on the rail- In the three sections of Amsteg, Sedrun quired, such as construction-plant power way track bed and the various built struc- North and Bodio West, the single-track supply, construction telecommunications tures. Temporary relocation of roads and tubes are already fully concreted along a and construction-site ventilation. These railway tracks was necessary. In the Erst- length of more than 40 km and ready for systems will be installed first. feld section, excavation of the tunnel installation of the railway infrastructure. The greatest challenge for installation of tubes was completed in mid-2009. Work In May 2010, installation of the railway the railway systems is the confined space on the two cut-and-cover tunnels, which systems began at the south portal of the of the Gotthard Base Tunnel. All materi- when completed will form the most Gotthard Base Tunnel in the Faido-Bodio als are brought entirely by rail into the tun- northerly section of the Gotthard Base West section, in parallel with completion nel through the two portals.. Access for Tunnel, is also progressing rapidly. The of the concrete shell in other sections of tired vehicles, and particularly turning Amsteg section has been ready for in- the tunnel. space in the 57-km-long tunnel, are very stallation of the railway infrastructure In the Faido-Bodio West section, a total limited. Two installation sites at Biasca in since December 2009. In the Faido and of more than 14 km of railway track, cate- the south and Altdorf/Rynächt in the Sedrun sections, the main focus of the nary and electric power supply systems north provide the logistical facilities for in- work in addition to the conclusion of are being installed as well as telecommu- stallation of the railway infrastructure. drilling is installation of the infrastructure nication and train control systems and More than 1000 technical interfaces must be coordinated to make trouble-free rail traffic in the Gotthard Base Tunnel possible. The material required includes 31000 cubic metres of concrete for the track bed, 308 km of rails, 3200 k of copper cable for the power supply, 417 emergency call columns, and 120 km of antenna cable for wireless communication.

Ceneri Base Tunnel Construction concept The Ceneri Base Tunnel also consists of two parallel single-track tunnels, which are linked at intervals of approximately 325 m by connecting galleries. With a length of 15.4 km, the Ceneri Base Tun- nel will have no track crossovers or multifunction stations. At the beginning of Fig. 4: In May 2010, installation of the railway infrastructure began in the west October 2010, a total of 39.78 km had tunnel in the Bodio section. been excavated representing almost 24%

6 AlpTransit Gotthard

wards the north and south in both tubes. Summary Inward drilling is also proceeding from the AlpTransit Gotthard is creating a future- portals in the north (Vigana) and south oriented flat rail link for travel through the (Vezia, near Lugano). All excavation Alps. Its central infrastructures are the two should be completed in 2015, after which base tunnels under the Gotthard and the railway infrastructure also will be in- Ceneri mountains. They will reduce the stalled in the Ceneri Base Tunnel. Com- time to travel by train from Milan to Zurich missioning is scheduled for 2019. to less than three hours. There will also be a marked improvement for rail-based Present state of work on the Ceneri freight traffic through the Alps. Base Tunnel The Gotthard Base Tunnel, with a length At Camorino, the area north of the north of 57 km between the north portal at Er- portal of the future Ceneri Base Tunnel, stfeld and the south portal at Bodio, and various undertakings have been carried with a rock overburden of up to 2500 m, out on built structures and subprojects is the world's longest and deepest tun- such as canals, bridges and underpasses. nel. The final breakthrough in the east These will form part of the link between tunnel took place on October 15, 2010. the Ceneri Base Tunnel and the existing Scheduled train services are planned to Swiss Federal Railways line. Tunnelling start at the end of 2017. The Ceneri Base work in the area of the north portal at Vi- Tunnel, with a length of 15.4 km, con- gana began in 2009. Because of the short nects Vigana in the north with Vezia, near vertical distance to the overhead A2 mo- Lugano, in the south. The first train should torway, this work had to be carried out be able to travel through the Ceneri in with special caution. The first blast for the 2019. main northward and southward tubes Fig. 5: Drilling holes for blasting by the took place at the Sigirino intermediate north portal of the Ceneri Base Tun- heading in March 2010. In April 2010 at nel. the south portal in Vezia, the first blast took place for the first approximately 300 of tunnels and galleries of the Ceneri Base m of tunnelling to the north. Also at the Dr. Renzo Simoni Tunnel. The Ceneri Base Tunnel is being south portal, because of the close prox- Chief Executive Officer dug entirely by conventional drilling and imity to residential and commercial infra- AlpTransit Gotthard Ltd. blasting. structure, including the late seventeenth- Zentralstrasse 5 The main tunnelling is proceeding from century Villa Negroni, drilling must be ex- CH-6003 Lucerne/Switzerland Sigirino, where the miners are working to- ecuted with special care. [email protected]

7 AlpTransit Gotthard

a base tunnel was revived. A commission AlpTransit: to study a road link across the Gotthard that could be kept open in winter rec- A European link through the ommended a highway line as well as a Gotthard railway base tunnel line. This fo- Swiss Alps cus on the Gotthard passage, however, provoked competing proposals further Railway lines through mountainous areas are unique: Their main purpose is not to east and west. Still, in 1970 the Gotthard provide access to the regions they traverse, but to link the regions that are divided by line was confirmed by the transalpine rail- mountains. If the regions lie in the same country, the railway line is a means to im- way tunnel commission (KEA). The then prove national cohesion. If the regions are located in different countries, however, the department of transport and energy line becomes of international interest. A combination of the two cases leads to chal- (EVED) published a concept in 1973 that lenges that result in unconventional decision making processes. At the Gotthard Rail- called for double tracking the Lötschberg way, this decision-making took place at a time when Swiss foreign relations were in line and, as a long-term plan, a Gotthard a delicate state. The transport flows transiting the Alps through Switzerland do not Base Tunnel. naturally follow a predetermined path, but three competing corridors exist: in the While the double tracking was complet- west, center and the east of the country. As the resources and demand would not ed between 1977 and 1992, interregion- justify the development of three parallel railway corridors, a choice had to be made. al disagreement continued, especially be- This choice was heavily influenced by the cantons and hampered by their disagree- tween Gotthard and Splügen, as the «east ments. alpine railway promise» made by the Bun- desrat in 1878 kept being cited. A joint group was not able to deliver a clear rec- clinations at acceptable levels. Finally, dur- ommendation. In the meantime, the tran- Prof. Dr. Ulrich Weidmann ing the construction of the Mont Cenis sit volume collapsed and, as a result, pres- railway, opened in the same year, decisive sure to act was lifted. Consequently, the 1845–1882: The realization advancements in tunneling techniques Bundesrat put the issue on hold in 1983. of the Gotthard Railway were achieved. With the opening of the Gotthard A2 In 1869, in a conflict-laden process, the highway in 1981, the success of the Got- With the Schöllenen gorge bridged, the politician and entrepreneur Alfred Escher thard railway was diminished: Passenger Gotthard pass became a significant trade led a new assessment of the Gotthard rail- numbers fell from 7 million per year in route and strategically important point, way, enabling political support after hav- 1979 to only 3 million in 2009. In freight although transport volumes at that time ing first favored a transit route to the east transport, the rail modal share fell from may seem negligible by today’s standards. of the Alps. Strategic interests of Italy and 90% to 65%. In 1999 rail freight was lib- Since 1845, even before the first railway Germany helped in this process, as they eralized, and the Lötschberg-Simplon line in the country was in operation, railway contributed CHF 45 million and CHF 20 gained more and more market share, fur- lines through the Alps have been studied. million, respectively, to the estimated ther reducing the Gotthard market share There were many doubts, however, and overall project cost of CHF 187 million. in Swiss transalpine rail freight from 75% the pioneers Stephenson and Swinbune, Options studied for the alignment in- to only 55%. referred to as federal consultants, dis- cluded a visionary base tunnel at 800 m couraged the implementation of alpine above sea level, as well as the use of very 1985–1994: Alpine transit railways in 1850. They may have been steep ramps with cable cars. When the decisions and the alpine caught up in the British design philoso- line opened in 1882, contemporary de- phy, which favored rather straightforward sign approaches similar to those applied protection clause alignments. At the time it had yet to be in other great alpine railways of the time When parliament discussed the Bahn proven that building such railway lines prevailed. 2000 infrastructure investment package was possible. in 1986, the alpine transit railway was still Three fundamental innovations paved the 1946–1983: Gotthard Base omitted. This left the cantons of Ticino way: First the Semmering railway of 1854 Tunnel projects without and Valais without a viable perspective for proved that inclinations of 25 ‰ and 190 an unknown length of time. Soon, polit- m radii were indeed manageable. Second, results ical motions called for a new transalpine in 1871 the Blackforest railway pioneered Despite technological advances, operat- route – and this time, the timing was right: deviations from topography and artificial ing the Gotthard railway remained cost- The increasing number of trucks dis- elongations of the railway line to keep in- ly. As a consequence, in 1946 the idea of proved the claim that the Gotthard high-

8 AlpTransit Gotthard

The law pertaining to alpine protection was also delayed and became active only in 2001. A modal shift goal was set, calling for a reduction in the number of trucks crossing the Alps to no more than 650,000 by 2009. While slight success was recorded in the beginning, the number of trucks increased again beginning in 2007, and the 2010 estimate was 1.3 million trips. Realizing that the goal of 650,000 is nearly impossible to achieve, the target year has been extended to 2019. Fig. 1: Sketch of an idea for the Gotthard Base Tunnel from Eduard Gruner, published in 1947 (Collection of the author). The Gotthard Base Tunnel way would serve mainly passenger traf- traffic should be by rail, from each end of and passenger transport fic. At the same time, the destruction of the Swiss border. After a heated contro- For rail passenger traffic, the Gotthard the protective forests took place, which versy preceding the vote, this initiative Base Tunnel will reduce travel times from was attributed to a general forest decay was approved with a 51.9% majority in the German part of Switzerland by an resulting from road traffic. During this sit- 1994 and is now article 84 of the feder- hour, thus creating a new landscape and uation, a call for unrestricted transit for al constitution. putting most of the Ticino within reach trucks up to 40 tons was made by the EU. for day trips from most of German During these conflicting issues, new 1995–2010: alpine railways became a political issue. Redimensioning and the The Bundesrat quickly had the proposed law to shift freight lines re-evaluated. Thirteen of the cantons favored the Gotthard, seven the transport Lötschberg, and six the Splügen. Under In 1992, freight transport profitability was the perceived pressure to act, the simul- at its peak; however, by 1996 it had de- taneous construction of two transit rail- creased by 25%. From 1994 on, doubts ways, Gotthard and Lötschberg, was then about profitability grew. In 1995, a red- announced in the 1990 alp transit dis- imensioning was commissioned: The patch and approved by the citizens in Lötschberg Base Tunnel was to be double 1992. tracked only in its southern third and on With this decision made, Switzerland was the Gotthard line; the second Zimmerberg able to obtain EU-agreement to raise the tunnel, a new line from Arth-Goldau to freight road tolls to their maximum level Erstfeld (including Urmiberg and Axen upon the opening of the Lötschberg Base tunnels) and the Bellinzona bypass were Tunnel and to keep the night and Sunday omitted. travel prohibitions for road freight trans- At that time, opening estimates were still port. However, an increase in the maxi- 2006 for the Lötschberg Base Tunnel and mum weight to 40 tons, commencing in 2008 for the Gotthard Base Tunnel, justi- 2005, had to be agreed upon. As a quick fying the capacity reduction of the for- measure, the Lötschberg line was up- mer. The completion dates slipped, how- graded to 4 m corner height in order to ever, and while full operations in the accommodate intermodal transports by Lötschberg base tunnel commenced in 2001. 2007, the Gotthard base tunnel will not For the regions directly affected, howev- be in operation until 2016 or 2017, and er, this was not enough. In 1989, the the Ceneri Base Tunnel will take until 2019 Fig. 2: Proposal 6c of the Commission «alpine initiative for the protection of the to complete. Consequently, the single- «Safe winter road link though the alps region from transit traffic» launched track at the Lötschberg now constitutes Gotthard» from 1963 (Collection of its campaign, demanding that all transit a significant bottleneck. the author).

9 AlpTransit Gotthard

The Gotthard Base Tunnel and freight transport

In the freight sector, the prospects are controversial: The Gotthard Base Tunnel by itself is unlikely to achieve the modal shift goal. While travel times and operational complexity for long freight trains decrease significantly, these improvements are not as large, seen in context with the long running times of those Fig. 3: The slightly different base tunnel project: TRANSAS study from the Fed- trains. Consequently, a market share gain eral Office of Transport (1972), car shuttle train with a top speed of 210 km/h of no more than 2.5% is expected. More (Collection of the author). important for today’s just-in-time logistics concepts are on-time performance and Switzerland. This will immediately im- from each other. A major change is ex- the degree of flexibility of train paths, re- prove the competitiveness of rail com- pected in the settlement patterns of quiring the railway infrastructure to pro- pared to road traffic. Already the demand southern Switzerland. Already an increase vide this flexibility. However, the previ- for the Lötschberg Base Tunnel has in- in investment activity has been observed ously mentioned redimensioning mea- creased by a third, and an even stronger in the vicinity of the major railway sta- sures create a series of bottlenecks on the effect is expected at the Gotthard. In the tions. Around the Lötschberg line, an in- lines leading to the Gotthard that can long term, 18 000 to 19 000 passengers creasing number of people living south of hardly be remedied, even with the next per day are expected; about the same vol- but working north of the Alps has been step in infrastructure development, ume as before the highway was opened. observed. Similar development is expect- namely, «future development of the rail- Most of this volume will come from do- ed with the completion of the Gotthard way infrastructure» (ZEB). mestic leisure and business travel, and to Base Tunnel, albeit to a smaller extent, as There are further issues complicating the a smaller extent from international travel the main centers of Lucerne, Zug and matter: About half a million trucks per between Switzerland and Italy. However, Zurich are still significantly more than an year bypass Switzerland, primarily using a significant volume of traffic is not ex- hour away. However, a major increase in the Brenner. Moreover, neighboring pected as the major population centers events such as conventions and seminars countries have little understanding of the north and south of the Alps are too far is expected. unique path Switzerland is taking with re-

Line Continuous Highest Minimaler Radius Apex height Apex length operation inclination [‰] [m] [m above sea [m] level]

Semmering 1854 25.0 190 898 1430 Brenner 1867 25.0 285 1371 – Mont-Cenis 1871 30.2 345 1298 13 657 Schwarzwald 1871 20.0 300 832 1698 Gotthard 1882 27.0 280 1155 15 003 Arlberg 1884 31.0 250 1311 10 250 Simplon 1906 25.0 300 705 19 803 Tauern 1909 27.0 250 1226 8551 Karwendel 1912 36.5 200 1185 – Ausserfern 1913 32.0 190 1128 512 Lötschberg 1913 27.0 300 1240 14 612 Tenda 1928 25.0 300 1073 8099

Table 1: Parameters of European mountain railways of the 1st Generation.

10 AlpTransit Gotthard

Fig. 4: Combined freight train on the Gotthard south ramp Fig. 5: NEAT as a key element for equalizing interests at Lavorgo (Photo SBB AG). among Switzerland, Europe and the affected regions (own Figure). gard to traffic in the alpine region. A con- portance in freight transport: It is part of EU’s transportation and environmental verging of social and safety standards be- one of the most important freight trans- goals than it might currently realize. tween rail and road freight is not ob- port corridors on the continent. It is be- served. Also, the introduction of 25 m ing financed by Switzerland entirely, how- information on the sources available by trucks with a maximum weight of 60 tons ever, and at the current train path fees, the author lobbied for by a number of European its usage by foreign transports will be countries would deal a blow to the eco- highly unprofitable. Its importance as a logically oriented transport policy of national passenger corridor prevails and, Prof. Dr. Ulrich Weidmann Switzerland. There is hope regarding this with respect to the spatial developments, Institut für Verkehrsplanung/ issue, however, as in some European the Gotthard Base Tunnel will even have Transportsysteme countries these longer vehicles are also a strong regional component. ETH Zürich the topic of public debates, and the EU In this light, the new European alpine Wolfgang-Pauli-Strasse 15 accepts the strategic importance of the transversal (NEAT) is best viewed as a link- CH-8093 Zürich Swiss alpine transit railways. Thus the ing element: It is the key element of the [email protected] railway corridor A, from Rotterdam to ongoing negotiations between Switzer- Genoa, has been selected to be the first land and the European Union and the re- one to be fully inter-operational by 2015. gions directly affected. Within this un- common situation in foreign affairs, Switzerland has found a very specific Conclusion Swiss answer. The success of this answer, Is the Gotthard Base Tunnel a European however, can hardly be controlled by transportation artery? It is, considering Switzerland. It is possible that the NEAT the history of its formation and its im- might be more of a touchstone for the

Mode of 2000 2001 2002 2003 2004 2005 2006 2007 2008 transport / axis

Road 8.9 10.4 10.6 11.6 12.5 12.9 12.9 14.2 14.6 Total rail 20.6 20.8 19.3 20.5 23.0 23.7 25.2 25.3 25.5 thereof Gotthard 16.8 16.0 16.2 15.5 15.5 thereof Simplon 3.8 7.0 9.0 9.8 10.0 Overall total 29.5 31.2 29.9 32.1 35.5 36.6 38.1 39.5 40.1 Table 2: Transported freight volumes over the Swiss Alps in million net tons (UVEK: Relocation Report January 2007 - June 2009).

11 AlpTransit Gotthard

account and modelled. Research activities Modern technologies and into refraction in tunnels, especially in the portal areas, have been carried out since concepts solving the geodetic 1997 using a mobile temperature gradient measurement system developed at challenges of AlpTransit the ETH (Fig. 3) (Hennes et al., 1999). During the period 1997–2001 a so-called With construction of the Gotthard Base Tunnel, the surveying experts were faced with dispersometer was constructed at the ETH new requirements in geodetic metrology. These could be achieved with innovative Zurich that allows refraction-free direc- ideas and the development of new surveying methods. Simultaneously to the staking tion measurements. The refraction free di- out and monitoring tasks, in particular in the 1990s, revolutionary developments took rection is computed from the difference place in the field of geodetic instrumentation that allowed achievements in accuracy of the angles of arrival of the red and blue and reliability otherwise unattainable. laser beam free of hypotheses (Fig. 4). The technical challenges, however, in gener- ating the two laser beams and the sub- sensors, submillimetre movements of the micron detection of the offset of the blue H. Ingensand dams and the slopes of the valleys could and red laserspot are very high. Thus, this be determined. Due to these monitoring technology has not been implemented in systems, further settlements during the geodetic instruments up to now but the Newly developed tunnelling could be stopped and coun- functionality of a dispersometer has been technologies for the teractions immediately taken. With the demonstrated in a PhD thesis (Böckem, metrology tasks of the new millennium laser-scanning technolo- 2001). Gotthard Base Tunnel gy mastered the tunnel measurements. In project 2002, the first experiments using laser The direction transfer in scanners to determine the tunnel geom- The former triangulation and trilateration etry and deformations were carried out. the vertical shaft of Sedrun methods for establishing a reference net- Meanwhile, laser scanning became a Another challenge of the Gotthard Base work (Elmiger et al., 1993) were replaced standard method in tunnel monitoring Tunnel was the direction transfer in the completely by GPS and then by GNSS (Fig. and documentation (Zogg, 2007). In ad- 800 m vertical shaft at Sedrun. Alterna- 1). In 2005, the ETH set a world record dition to these technologies a so-called tive solutions such as direction transfer us- with simultaneous measurements using Tubemeter was developed at the ETH in ing polarized light, double plumbing, or 28 GNSS receivers to check the existing 1997 in the course of a study on risk min- a spatial trilateration network along the reference network (Ryf, 2006). Precision imization (Fig. 2). This instrument deter- wall of the vertical shaft had to be rejected digital levels, which have been produced mines the geometrical deviation in a test for reasons of accuracy and. cost. Hence, since 1995 by all major manufacturers, drilling before the breakthrough. Techno- only the transfer using north finding gy- are indispensable in today’s high precision logically the Tubemeter can be regarded roscopes, as they were originally devel- measurements. The minor height differ- as a «gliding» polygon. The height dif- oped for measurement in mines, was left. ences at the final breakthroughs of the ferences are continuously determined by But it has to be taken into account that tunnels speak for the accuracy of this new inclination measurements. gyroscopic measurements are systemati- technique based on image processing. Es- cally affected by external influences such pecially for the height measurements in as temperature and deflections of the ver- tunnels, homogeneous illuminations for Solving the refraction and tical that are in turn derived from gravity levelling staffs had to be developed. With turbulence effects in models. Thus, since 1997 measurements the use of digital levels it also became pos- using an inertial navigation system have sible to detect any settlement above the tunnelling been considered as an independent di- Gotthard road tunnel (swisstopo, 1998). With the use of today’s high precision op- rection transfer method (Fig. 5). The ef- The settlement monitoring systems of the tical instruments come detrimental sys- forts of the Technical University of Munich dams of Nalps, Cunera, St. Maria and the tematic and stochastic effects on the mea- to perform the direction transfer using an surrounding surface would have been un- surements caused by external atmos- inertial system in the Olympic Tower con- thinkable without a new generation of pheric influences in the form of refraction firmed the expectations of experts that an motorized and automatically pointing and turbulence. In particular, in tunnels inertial system can provide the same ac- tacheometers. With these instruments, in and the optical monitoring of dams these curacy as the gyroscope (Neuhierl et al., combination with GPS and geotechnical influences are to be carefully taken into 2006).

12 AlpTransit Gotthard

Fig. 3: Temperature gradient measu - rement system.

Fig. 1: Progress in metrology technologies vs. the construction phases of the Gotthard Base Tunnel.

The comparison of these measurements 6)) was developed within the terms of a Fig. 4: Principle of the ETH disper- carried out in 2004 and 2005, resulted in project financed by the Commission for someter. a difference of 2.2 mgon compared to the Technology and Innovation (CTI) (Glaus, gyroscopic measurements. 2006). SwisstrolleyTM has been success- ley in connection with precision fully used in the Thalwil Tunnel, being part tacheometers. For the track measure- Kinematic track surveying of the feeder route to the Gotthard Base ments in the Lötschberg Tunnel, the Tunnel. In the so-called slab track tech- UniBw München kinematically measuring technology nique, a submillimetre accuracy for the RACER system was used and is used in For the installation of the rail tracks, Swiss- staking out procedure is required. This ac- the Gotthard Base Tunnel now. trolleyTM (a track measurement trolley (Fig. curacy is achievable using this track trol- Summary The AlpTransit project with its requirements for high accuracy and reliability initiated an important progress in the de-

Fig. 5: Direction transfer using IMAR Fig. 2: Design of the ETH Tubemeter (1997). inertial navigation system.

13 AlpTransit Gotthard

Fig. 6: SwisstrolleyTM (terra) and RACER (UniBw). velopment of instruments and the com- Hennes, M., Dönicke, R., Christ, H. (1999): Zur ic high-accuracy measurement systems. Diss. putation of measurements. In addition, Bestimmung der temperaturgradientenin- ETH No 14252. the permanent monitoring systems for duzierten Richtungsverschwenkung beim Tun- Swiss Federal Office of Topography Swisstopo dam and terrain observations led to im- nelvortrieb. VPK, 8/99, S. 418–-426. (1998): Bodensenkungen über dem Gotthard- proved scientific knowledge and new the- Glaus, R. (2006): The Swiss Trolley – A Modu- strassentunnel. Presse Mitteilung 22.1.1998. ories. With the successful tunnel break- lar System for Track Surveying. Geodätisch- through, the performance of geodetic geophysikalische Arbeiten in der Schweiz (SGK), Band 70. measuring techniques and the modelling of particular factors in tunnels has been Zogg, H.-M. (2007): Terrestrisches Laserscan- demonstrated. ning zur Aufnahme von technischen Bauw- erken am Beispiel von Schachtkammern. In: Beiträge zum 74. DVW-Seminar «Terrest - risches Laserscanning – Ein Messverfahren er- Prof. Hilmar Ingesand References: obert den Raum» (Red.: Barth/Foppe/Schäfer), Geodätische Messtechnik und Neuhierl, T., Ryf, A., Wunderlich, T., Ingensand, Fulda. Ingenieurgeodäsie H. (2006): AlpTransit Sedrun: Weltpremiere mit Elmiger, A., Köchle, R., Ryf, A., Chaperon, F. Institut für Geodäsie und inertialer Messtechnik. Geomatik Schweiz, (1993): Geodätische Alpentraverse Gotthard. Photogrammetrie 6/2006. Geodätisch-geophysikalische Arbeiten in der ETH Zürich Ryf, A. (2006): Gotthardtunnel: Weltrekord. Schweiz, Nr. 50. Wolfgang-Pauli-Strasse 15 Reporter 55: Das Magazin der Leica Geosys- Böckem, B. (2001): Development of a disper- CH-8093 Zürich tems. Heerbrugg, Oktober 2006. someter for the implementation into geodet- [email protected]

14 AlpTransit Gotthard

Accuracy and Tolerance Geodetic Basis and Main The main task and responsibility is steering the drive (tunnel-boring machine and Control Surveys in the blasting) at a transverse and longitudinal accuracy of 10 cm and 5 cm in height. As Gotthard Base Tunnel customary in surveying, this accuracy requirement is defined as one standard de- This article summarizes the surveying work of the Gotthard Base Tunnel Surveys Con- viation (1s) in a statistical sense. The consortium from 1995 to 2010. Beginning with the contractual requirements, the geo- tract stipulated a maximum acceptable er- detic basis and the establishment of the reference frameworks NetzGBT_Lage and ror (tolerance, worst case) of 2.5 s and NetzGBT_Höhe are described. The concept of tunnel surveying, the performance and confidence intervals of 95% for position processing of tunnel controls and the survey of the 800 m Sedrun vertical shaft are and 99% for height. This results in a max- presented. The analysis of survey data and the appraisal of accuracy and reliability are imum acceptable transverse and longitu- explained. The theoretically expected breakthrough accuracies (breakthrough prog- dinal surveying error of 25 cm and 12.5 nosis) of the four main breakthroughs in the Gotthard Base Tunnel and the actually cm in height. In other words: «In order to achieved breakthrough results are compared and assessed in a historic context. meet the accuracy requirements in more than 20 km long tunnel sections, the transverse and longitudinal error per 100 m must not exceed 1 mm, and the height error may even amount to 0.5 mm only.» 3. Densification of the control network in R. Stengele, I. Schätti-Stählin 5 portal areas 4. Measuring concept for tunnel survey- 2. Control Network 1. Tasks and ing (Position): NetzGBT_Lage Responsibilities of the 5. Periodic heading controls and main Consortium Gotthard Base control surveys as a basis for the steer- The aboveground control network is coming control in position and height prised of 28 main survey points spread Tunnel Surveys (VI-GBT) 6. Verticality measurements in the 800 m over the portal areas. They were perma- The Gotthard Base Tunnel Surveys Sedrun shaft nently marked on geologically stable rock Consortium 7. Choice of breakthrough zones opti- and were measured with GPS for the first In 1995, the Gotthard Base Tunnel Sur- mized for surveying time in 1995 in accordance with the state veys (VI-GBT) Consortium applied for the 8. Permanent monitoring surveys (subsi- of the art at that time. To increase both planning and performance of the geo- dences, shifts) underground and above accuracy and reliability, one point of the detic works in the NEAT lot «Gotthard ground National Survey LV95 was included in the Base Tunnel». This Consortium brings to- 9. Control surveys of the completed con- vicinity of each of the five portals. A gether the know-how of four Swiss engi- struction: profiles, shoulders, shafts, Helmert transformation of the high-pre- neering and surveying companies with a blanket-coverage laser scanning, track cision, free GPS network to the connec- total of 120 employees: beds and railway systems. tion points in the area of the main por- • Grünenfelder und Partner AG in Do- In conjunction with additional publica- tals in Erstfeld and Bodio minimized the mat/Ems tions, this article provides an overview of positional differences to existing net- • BSF Swissphoto AG in Regensdorf tasks 1 to 6. In a project with a time frame works (cadastral surveying, Swiss Federal • Studio Meier SA in Minusio of 20 years, concepts and technologies Railway networks) without diminishing •Studio Gisi SA in Lugano need to be continuously adjusted to new the inner accuracy of the GPS control net- developments. This requires innovation, work. Based on the adjustment of all mea- Tasks and Responsibilities process orientation and meticulous surements, the accuracy of the «Netz - Having won an international bidding knowledge management at all levels. Pro- GBT_Lage» was estimated at 1sy,x< 7 competition in 1995, the Consortium was ject and quality management are a key mm and 1 s position < 10 mm, respec- entrusted with the responsibility for the competency and pose – apart from the tively. The relative accuracy between two following tasks by the AlpTransit Gotthard purely technical requirements – a huge random points is < 10–6 in all cases. Back- AG: challenge for the project managers in up markings at all points of the basic and 1. Geodetic basis charge. portal networks allowed for the monitor- 2. Aboveground control network for po- ing of local shifts over the project dura- sition and height tion of 20 years.

15 AlpTransit Gotthard

In summer 2005 – that is 10 years after The Federal Office of Topography (swiss - tunnel section along the tunnel axis and the establishment of the control network topo) was already working on the elimi- in the 800 m deep vertical Sedrun shaft and one year after the first main break- nation of these weaknesses in the course by means of mass, density and gravity through in Bodio-Faido – a complete re- of the renewal of the national levelling models (Fig. 2). The various model based peat measurement of the GPS control net- and the establishment of the new height corrections in the height system added up work took place. With the co-operation reference framework LHN95. Work on to more than 10 cm in certain tunnel sec- of VI-GBT and ETH Zürich, the entire net- LHN95 in the geographic area of NEAT tions. They clearly exceeded the required work was measured «in one go» with 28 was therefore prioritized and closely co- height accuracy and even the accuracy at GPS receivers. Except for one point, the ordinated between swisstopo and VI-GBT. which height differences can be levelled positional differences between the mea- All national levellings carried out in the in the first place. The model of uplift of surements of 1995 and 2005 fell within last decades were digitised, gravimetri- the Alps alone (vertical speed = 1.2 mm/y the 95% confidence interval. cally reduced and strictly adjusted using a in Ticino, 0.8 mm/y in Sedrun) results in a Also in summer 2005, the Swiss Gravity kinematic model for the uplift of the Alps. height difference of 7 mm in the Faido- Field Consortium (SKS), in co-operation By applying this method, the complex pre- Sedrun tunnel section over a time frame with ETH Zürich and the Institute of Ge- cision levellings could be limited to ap- of 15 years, which represents more than odesy of the University of Hannover, car- proximately 30 km of connection level- 10% of the required height accuracy. ried out astro-geodetic measurements lings from the portals to the national lev- Of course, the numerous height correc- checking the orientation of each portal elling network. An excellent synergy tions (orthometric correction, uplift of network. Direct comparisons of azimuths developed through synchronization of the Alps extrapolated to the time of break- measured astronomically and reduced in- interests of the National Survey with those through, network embedding deficien- to the projection plane with azimuths of of the Gotthard Base Tunnel project! cies) were not suited for practical imple- NetzGBT_Lage showed an orientation dif- With the definition of the height refer- mentation on the construction site. This ference of approx. 1 mgon between Er- ence framework for the Gotthard Base is why linear overall corrections were cal- stfeld und Bodio. The orientation differ- Tunnel (NetzGBT_Höhe), it followed that culated for each tunnel section and ap- ences between the «neighbouring» por- the effect of the gravity field on all un- plied by VI-GBT to the underground tals were < 0.3 mgon. Furthermore, derground measurements had to be tak- height measurements. This way, all other astro-geodetically determined vertical di- en into account in the form of orthome- parties involved in the project were spared rections were compared to those of the tric corrections. Orthometric corrections the problem of height correction. CHGeo98 geoid model (Fig. 1). Based on and the resulting theoretical loop closing In summer 1995, the (not hypothesis free) these results, one could safely assume errors (non-parallelism of equipotential gravity model used by swisstopo was re- that the gaug-ing/calibration/reduction of surfaces Ǟ path dependence of levellings) viewed by gravimeter measurements per- the geographic gyro azimuths could be were calculated by swisstopo for each formed by ETH Lausanne in the already done without systematic errors.

3. Control Network (Height): NetzGBT_Höhe It was clear to VI-GBT, even in the proposal phase, that complete precision levellings across several alpine passes as a direct connection between all five portals was out of the question for economic reasons. It was equally clear that the existing national levelling network was unsuitable as a height reference system for the stake out of the Gotthard Base Tunnel for several reasons: «working heights», no heights strictly reduced in accordance with potential theory, no overall adjustment of levelling loops, no consideration of recent crustal movements, and known inconsistencies (between Amsteg-Sed - Fig. 1: Topgraphy, geoid and components of deflection of the vertical on the run, 8 cm height gap in Ticino). Gotthard Base Tunnel axis

16 AlpTransit Gotthard

completed tunnel sections in Bodio and Sedrun. Differences between model Non-parallelism of equipotential surfaces based and measured gravities of < 3 mGal => path dependence of geometric levelling with an (theoretical) effect on the break- => consideration of theoretical loop closing error through error of < 1 mm were determined in the Bodio section. In particular the very good coincidence in the vertical Sedrun shaft was acknowledged very favourably at that time. In view of the complexity of height determination based on geophysical and geometric measurements in Europe’s ge- ographically and topographically most challenging region, the excellent breakthrough results in height are highly remarkable, and they constitute a real performance record for everybody involved in the conceptual design and implementation of the height reference framework NetzGBT_Höhe. Fig. 2: Model based orthometric corrections and loop closing errors of leveling. 4. Underground Control Network: Tunnel Surveying tunnels complicate this task considerably. • Parallel precision traverses in both sin- The reference frameworks «NetzGBT_ The special refraction problem due to the gle-track tunnels, with connection mea- Lage» (position) and «NetzGBT_Höhe» substantial temperature gradient at the surements between every 3rd or 4th tra- (height) provided the basis for the under- portal is alleviated by additional mea- verse point ground tunnel network and, with that, for surements of temporary support points in • Strict placement of traverse points in the the stake out of the tunnel axis and the the immediate vicinity of the portal (few middle of the tunnel at intervals of 400 control of the TBM and blasting headings. metres outside and inside). to 450 m. The initial situation for the tunnel survey • Overlapping sightings, i.e., measure- Importance of Portal Networks in the entry area of the tunnel is as fol- ments to the nearest two traverse points Both in the literature and during practical lows: in both directions, sighting distances work on the construction site, great im- Coordinate accuracy: 1 s (y, x, H) < 10 not more than 900 m. portance is attached to maximizing the mm, azimuth accuracy: 1s (azimuth) < • Gyro support of the traverse after every accuracy and increasing the reliability of 0.5 mgon. With that, the acceptable 5th to 7th traverse point (every 2 to 3 km). control networks and tunnel networks. transversal deviation would be reached Multiple determinations of mutual gy- The interface between aboveground and with a (theoretical) sighting length of 11.4 ro azimuths on the same traverse sec- underground surveying in the portal area, km. tions in different measurement cam- however, is neglected all too often, in the- paigns. ory as well as in practice. The accuracy po- Underground Surveying Concept • Height transfers by precision levelling tential can only be fully exploited if scale There are numerous concepts and meth- (to/from); control by trigonometric lev- and orientation of the control network is ods for the design and implementation of elling of the traverse. transferred underground via the portal polygon networks. All of them aim at min- • In curves: shifting of the traverse points area without any significant loss of accu- imizing the unfavourable error propaga- by max. 1 m outwards, reduction of dis- racy. This challenge is frequently under- tion in elongated traverses and the sys- tance between points down to 300 m, estimated, and unfavourable conditions tematic effects of dangerous horizontal compliance with >1.5 m sighting dis- in the portal area are more often the rule refraction. However, a generally accepted tance from tunnel wall, no overlapping rather than the exception: challenging scientific consensus – that is, the optimal sightings. topographic settings, ever-changing site solution - doesn’t exist. The VI-GBT opt- • Alternating deployment of staff and installations, ventilation equipment, site ed for the following surveying concept equipment (particularly gyro instru- traffic, local deformations, limited visibil- (Fig. 3) in 1995 and has adhered to it con- ments) in order to minimize systematic ity and narrow curve radii in the access sistently over the course of 15 years: effects.

17 AlpTransit Gotthard

Pre-analysis ferent points of time were available at By means of a network simulation (pre- every traverse point. analysis) it was verified a priori that the Usually, an independent azimuth control surveying concept would meet the re- with the precision gyro Gyromat-2000 quired accuracies in position and height. was carried out In the course of the «large The essential parameters of the stochas- tunnel controls». Mutual azimuths of two tic model were defined as follows: to three traverse sides were measured underground on each mission. In order to • Directions 3 cc ensure that controls of gyro measure- • Distances 0.5 mm + 1 ppm ments were as independent as possible, • Gyro azimuths three different gyros were used alter- Fig. 3: Underground surveying con- (single nately: DTM Essen, Bundeswehr Universi- cept. measurements) 15 cc ty of Munich and ETH Zürich. For the same • Centering 0.5 mm reason, measurement campaigns were met (resolution 1:200 000 = 0.5 mm per • Leveled height strictly separated from data analysis and 100 m), see Figs. 4 and 5. Three plummet differences 1.0 mm/km processing. corridors were measured in order to im- • Coordinate transfer Underground measurements always take prove accuracy and reliability. Their in the 800 m deep place under tough conditions. Apart from arrangement was determined by the ex- Sedrun shaft 24 mm permanent time pressure, unfavorable isting shaft installations. Prisms with cen- («3 mm conditions (visibility, light, noise, temper- tric light-emitting diodes, staked out with per 100 m») ature, humidity, ventilation, traffic…) as approximate coordinates at the bottom It is very important to make rather con- well as logistic and safety-related re- of the shaft, served as targets. The preci- servative assumptions in simulations in or- straints are common. A time window of sion positioning on the tripods was done der to make allowances for the below par only 12 h was available for the small tun- with cross slides (two axis slide tables). underground measurement conditions. nel controls. Large tunnel controls were usually carried out during scheduled con- Mechanical Plumbings Scope of Tunnel Controls struction breaks (Christmas/New Year, The mechanical plumbing was conduct- As soon as two (max. three) new traverse Easter, summer vacation). ed through three corridors as well. The in- points had been marked out in the con- stallations of the winches, the deflection crete floor – that is after tunnelling 1300 5. Surveys in the 800 m pulleys and the insertion of the 800 m m at the maximum –the coordinates were long plumb wires used up an entire work- determined by VI-GBT in the course of a Vertical Sedrun Shaft ing day (Figs. 6 and 7). Loading each wire «small tunnel control». The new points At the intermediate access point Sedrun, with discs weighing 390 kg completed the were linked to at least three of the near- tunnelling to both north and south start- installation. After letting the plumb bobs est existing traverse points, which resulted at the bottom of an 800 m deep shaft. rest for 12 hours, measurements were ini- ed in a traverse measurement of 2 to 2.5 The position transfer from the cavern at tiated the next morning. Using two km. After every 3 km of tunnel drive a the head of the shaft down to the level theodolites on two stations, 10 reversal «large tunnel control» was performed of the tunnel was realized in 2002 using points of the three oscillating plumb bobs with a traverse measurement spanning 8 two different methods: one optical and were measured in both telescope posi- to 10 points, which is over a length of 3.5 one mechanical. With the construction of tions. The second measurement series to 4.5 km. the second shaft in 2004, an opportuni- was acquired after reducing the weights In every tunnel section, an additional «half ty emerged to perform an additional op- to 192 kg, and the third again with the time control» was performed after reach- tical plumbing 39 km south of the first full load of 390 kg. ing approx. 50% of the total drive length. shaft. In January 2007, barely one year Additionally, an overall control was car- before the Amsteg-Sedrun breakthrough, Model for the Correction of ried out approx. 1.5 km before reaching an additional optical control plumbing Deflection of the Vertical the boundary of the lot. Half time and took place. With that, three optical and During the point transfer, the deflection overall controls included measurements in one mechanical plumbing were available of the vertical directly affects the accura- the portal network and the entire under- for the point transfer. cy of the coordinates; its consideration is ground tunnel network. therefore absolutely essential. Further- This scenario ensured that measurements Optical Plumbings more, the plumb line is curved, and the stemming from at least four different tun- The optical plumbing from the top to the correction values at the top and the bot- nel controls and performed at very dif- bottom was done with a Leica nadir plum- tom of the shaft differ (Figs. 8 and 9). The

18 AlpTransit Gotthard

better accuracy than anticipated. Here, too, it is worth mentioning that the model-based corrections from deflection of the vertical and plumb line curvature exceeded the actual accuracy of the plumbing several times. The accuracy of the height transfer

through the 800 m shaft is 1 σ ΔH= 3 mm. An azimuth for a 39 m basis differing only by 0.2 mgon from the gyro azimuth (mean value from several campaigns) was the result of the plumbings in both shafts.

6. Adjustment of Tunnel Fig. 5: Positioning of tripods at bot- Fig. 4: Nadir plummet at head of shaft. Networks and tom of shaft. deflection of the vertical was determined Breakthrough Prognosis As an average of all tunnel controls in all at an accuracy of 0.3 mgon using the soft- Accuracy of Observations sections, the following a posteriori ob- ware CHGeo98. Deflections of the verti- All adjustments of tunnel networks were servation accuracies were found for the cal and plumb line curvature resulted in done for position and height with the main variance components: correction values for the coordinate trans- LTOP software from swisstopo. After the • 12,406 direction fer of up to 34 mm. preparation of the raw data (set mean val- measurements 2.7 cc ues, meteo reduction, etc.), the quality of • 2809 gyro azimuths Results of Plumbing Measurements the observations in each tunnel control (single measurements, The immediate comparison of all plumb- was assessed by virtue of a free adjust- not averaged) 10.8 cc ing measurements showed a variation of ment. • 11600 distance < 20 mm. The inner accuracy of a plumb- It turned out that the frequency distribu- measurements 1.6 mm/km ing campaign was determined by com- tions of the normalised corrections ap- paring the congruence of the two trian- plied to the observations came very close Calculation of Coordinates gles formed by the three plumbing corri- to the theoretical normal distribution in Each coordinate calculation was made by dors at the top and at the bottom of the all tunnel sections (Fig. 10). virtue of an overall adjustment, thus shaft. For the overall adjustment, the me- Also, the general comparison of variances seamlessly adjusting all measurements of chanical plumbings were introduced at an «a posteriori vs. a priori» of all observa- all relevant tunnel controls. Measure- accuracy of 1 σ ΔyΔx = 5 mm, and the options (global test according to Baarda) ments in deformation areas were exclud- tical plumbings at 1 σ ΔyΔx = 10 mm. Thus confirmed that the choice of the sto- ed in advance from the overall adjust- the plumbing methods achieved a much chastic model was right and appropriate. ment. A slight decline of the inner accu-

Fig. 6: Deflection pulley with plumb wire. Fig. 7: Plumb bobs with 192 kg loads.

19 AlpTransit Gotthard

plumb-line direction Optical plumbing from top to bottom Optical plumbing from top to bottom North-eouth component West-east component Line of sight east Line of sight north deflection of Deflection of the vertical: 2.7 mgon Deflection of the vertical: 1.5 mgon the vertical

sea level topography Correction for Correction for plumbing: plumbing: dx = -34 mm dx = -34 mm

geoid

ellipsoid Mechanical plumbing from bottom to top Mechanical plumbing from bottom to top North-south component West-east component Line of sight east Line of sight north Fig. 8: Plumb-line direction and plumb-line curvature. racy as a result of small, non-significant Correction for Correction for plumbing: deformations between epochs was ac- plumbing: dx = 13 mm cepted in favour of high redundancy. dx = 25 mm Only points of portal networks were introduced as fixed points, which resulted in the statistically most probable solution for all underground traverse points. Re- Deflection of the vertical: 2.0 mgon Deflection of the vertical: 1.1 mgon peated coordinate changes, however, resulted in considerable complications on Fig. 9: Correction of plumb-line curvature for coordinate transfer in vertical the construction site and in discontinu- shaft. ities in the control system of the tunnel boring machines. For this reason, a spe- error propagation, the growth of error el- whether the entire conceptual, theoreti- cial method for «smoothing» the correc- lipses, typical for tunnel networks with in- cal, and practical work of the survey team tions was developed, with which the co- creasing drive length, could be observed. over the course of several years was suc- ordinate changes could be limited to 2 cm The expected theoretical breakthrough cessful or not. Although all efforts aim at at most. error was calculated as a relative error el- realizing the best possible result using the A target-group specific documentation lipse between the two traverse points of most accurate sensors, the best geodetic and a result reporting process were es- both drives located closest to the break- data, and the most reliable measuring and tablished. The contractor was supplied through point (Fig. 11). The following pre- adjustment concepts, residual risks and with condensed reports with the current- diction for the four main break throughs doubts remain until the last metre is bro- ly valid coordinates of traverse points. in the Gotthard Base Tunnel was made ken through (Fig. 12). The following ac- Measurements and adjustments of large immediately before the breakthroughs: curacies were achieved in the Gotthard tunnel controls were documented in tech- «The probability is 95% that the break Base Tunnel: nical reports submitted to ATG Geomatik through error does not exceed the fol- Depending on the professional back- and to external experts for review. lowing values:» ground and point of view, these break throughs are assessed in very different Appraisal of Underground ways: Accuracy and Breakthrough 7. Breakthrough Results in • From the construction point of view of Prognosis the project engineer: «The break- The accuracy of the position and height the Gotthard Base Tunnel through errors can be compensated for of traverse points could be estimated In tunnel construction, breakthroughs are when installing the vault. Expensive pro- based on the overall adjustments of the huge events in many respects. On break- file corrections are not necessary.» tunnel networks. Due to the unfavourable through day it becomes apparent • From the dynamic point of view of the

20 AlpTransit Gotthard

• From the point of view of the insurance Section Length # of Unknowns error company: «The residual risks were un- [km] measurements quotient der control. There are no liability issues.» • From the point of view of the con- 7535 2149 0.80 Bodio–Faido 19.8 2364 821 0.53 struction lawyer: «There are no obvious surveying errors. But, are we really sure 9499 2820 0.92 that everything was done right and with Amsteg–Sedrun 17.3 4379 1170 1.10 due diligence fitting to a once-in-a-century event?» 2846 742 1.19 Erstfeld–Amsteg 10.1 • From the point of view of the technol- 1350 284 1.17 ogy minded ignoramus: «What was the problem? Nowadays, that shouldn’t be 7205 1991 0.80 Sedrun–Faido 23.4 a problem with all that GPS and laser, 2478 799 0.62 right?» Table 1: Observation accuracy and und error quotient a posteriori vs. a priori. • From the point of view of the geode- sist: «Our models are not so bad, ap- parently. The result validates our work • From the point of view of the prosaic of the last years.» statistician: «The results meet the ex- • …And from the point of view of the sur- pected values quite accurately.» veyors in charge: «We have used less

Section length transverse longitudinal height [km] [cm] [cm] [cm]

Bodio–Faido 19.8 < 22 <8 <6 Amsteg–Sedrun 17.3 < 22 < 10 <6 Erstfeld–Amsteg 10.1 < 15 <9 <5 Sedrun–Faido 23.4 < 27 < 13 <7

Table 2: Breakthrough prognosis a priori (95% confidence level) for the four main breakthroughs.

Date Section lengths trans- longi- height incl. access tunnels verse tudinal [mm] and shafts [mm] [mm] [km]

Faido 4.1 22.08.2006 19.8 92 12 17 Bodio 15.7

Amsteg 13.3 14.10.2007 17.3 137 21 3 Sedrun 4.0

Erstfeld 7.8 16.06.2009 10.1 14 33 5 Amsteg 2.3 Fig. 10: Normalized corrections of observations in the sections Sedrun Sedrun 15.0 15.10.2010 23.4 81 136 11 (above), Faido (middle), and Bodio Faido 8.4 (below). Utilization of max. tolerance (average) 32% 20% 7% track builder: «Breakthrough errors can be compensated for by slightly distort- Table 3: Breakthrough results in the four main breakthroughs of the Gotthard ing the rails.» Base Tunnel.

21 AlpTransit Gotthard

Carosio A. (2010): Die Vermessung des längs - ten Eisenbahntunnels der Welt. Die Sicht des Experten des Bauherrn. Geomatik Schweiz, Ausgabe Dez. 2010 Ebneter F. (2004): AlpTransit Gotthard: Auf- gaben und Organisation der Vermessung. XIV. Internationaler Kurs für Ingenieurvermessung, Zürich Gesellschaft für Ingenieurbaukunst (1996): Historische Alpendurchstiche in der Schweiz: Gotthard – Simplon – Lötschberg.. Haag R., Stengele R. (1997): The Gotthard- Basetunnel. Surveying of a 57 km long Un- derground Project in the Swiss Alps. FIG-Sym- posium «Surveying of Large Bridge and Tun- nel Projects», Kopenhagen Kobold F. (1982): Vor hundert Jahren: Die Absteckung des Gotthard-Basistunnels. Ver- messung, Photogrammetrie, Kulturtechnik 3/1982. Fig. 11: Breakthrough prognosis and breakthrough error of 1st main break- Kobold F. (1981): Tunnelabsteckungen im Got- through Bodio-Faido. thardgebiet von Koppe bis zur Gegenwart. Deutsche Geodätische Kommission bei der Bayerischen Akademie der Wissenschaften, than 1/3 of the maxi-mum acceptable been published. Further publications can Reihe E, Heft Nr. 20. tolerances. We always knew that we be downloaded from www.bsf-swisspho- Korittke N. (1997): Zur Anwendung hoch- were on course with our accurate and to.com. präziser Kreiselmessungen im Bergbau und reliable concepts and our proven qual- Carosio A., Reis O. (1996): Geodetic Methods Tunnelbau. Geodätische Schriftenreihe der ity management. Nevertheless, we are and Mathematical Methods for the Establish- Technischen Universität Braunschweig, Nr. 14. relieved and pleased that the worst case ment of New Trans-Alpine Transportation Riesen H.-U., Schweizer B., Schlatter, A., Wiget didn’t occur.» Routes, Bericht IGP No. 206, ETH Zürich A. (2005): Tunnelvermessung des BLS-Alp- The breakthrough results achieved in the Gotthard Base Tunnel can also be assessed in a historic context

8. Acknowledgements Surveying is teamwork! The Consortium Gotthard Base Tunnel Surveys co-operated very closely with a variety of organizations and companies over the past 15 years (Fig. 13). All these partners have contributed to the good results in the Gott hard Base Tunnel. We would like to extend our thanks in particular to the project managers F. Ebneter and A. Ryf from AlpTransit Gotthard AG, and to the expert Prof. em. A. Carosio for the trusting and goal-oriented co-operation.

9. Literature A vast number of publications on the surveying in the Gotthard Base Tunnel have Fig. 12: Boring head of tunnel boring machine at breakthrough.

22 AlpTransit Gotthard

Transit Lötschberg-Basistunnels. Geomatik Date Section length transverse longitudinal height Schweiz 11/2005. incl. Schätti I., Ryf A. (2004): Hochpräzise Lotung access im Schacht Sedrun des Gotthard-Basistunnels. tunnels XVI. Internationaler Kurs für Ingenieurvermes- and sung, Zürich shafts [km] [cm] [cm] [cm] Schätti I., Ryf A. (2007): AlpTransit Gotthard- Basistunnel: Grundlagenvermessung, letzte 28.02.1880 Gotthard-Bahntunnel 15.0 33 710 7 Kontrollen vor dem ersten Durchschlag. XV. In- ternationaler Kurs für Ingenieurvermessung, 24.05.1905 Simplontunnel 19.8 20 < 200 9 Graz 31.03.1911 Lötschbergtunnel 14.6 26 41 10 Stengele R. (2007): Erster Hauptdurchschlag 01.12.1990 Eurotunnel 37.9 36 76im Gotthard-Basistunnel: Tunnelvermessung in Theorie und Praxis. XV. Internationaler Kurs 28.04.2005 Lötschberg-Basistunnel 34.6 für Ingenieurvermessung, Graz. Mitholz-Ferden 20.9 13 10 0 Stengele R., Ryf A., Schätti I., Studer M., Salvi- Gotthard-Basistunnel 57.0 ni D. (2010): Vermessung im Gotthard-Basis- tunnel: Vortriebsvermessung, Laserscanning, 22.08.2006 Faido–Bodio 19.8 912 Langzeit-Monitoring. XVI. Internationaler Kurs 14.10.2007 Amsteg–Sedrun 17.3 14 20 für Ingenieurver-messung, Graz. 16.06.2009 Erstfeld–Amsteg 10.1 130 Zanini M., Stengele R., Plazibat M. (1993): 15.10.2010 Sedrun–Faido 23.4 8 14 1 Kreiselazimute in Tunnelnetzen unter Einfluss Table 4: Results of major Alpine breakthroughs and the Eurotunnel. des Erdschwere-feldes, Berichte des Instituts für Geodäsie und Photogrammetrie der ETH Zürich, Nr. 214.

Roland Stengele BSF Swissphoto AG Ivo Schätti-Stählin Studio Meier SA Dorfstrasse 53 Postfach CH-8105 Regensdorf-Watt Fig. 13: Partner and network of VI-GBT. roland [email protected]

23 AlpTransit Gotthard

od of 20 years. It was our aim to collect The (surveying) challenges at the data digitally and to ensure their continuous updates until the end of the con- the beginning of the project, struction works. An early and simplified data collection covering our project when everything was new and perimeter was arranged with the institutions of the official cadastral survey. These unknown institutions disposed of a big part of the data in graphic form on the basis of the At the beginning of the 1990s, when the survey work for the new Alpine Rail Tunnel land register survey and were, at the time, at the Gotthard had to be organized and developed, many things were in transition. launching the «cadastral surveying re- With the reform of the official cadastral system, the introduction of the new national form project» (RAV). Digital data of surveying system, the development of new automated measuring instruments and ground cover and terrain models were corresponding evaluation programs or new possibilities of data communication, the created from photometric images and manifold surveying needs could be optimally realized. This article shows that the chal- their analysis. The boundaries and further lenges at the beginning of the project with the development of the surveying orga- information were digitalized from graph- nization, the delegation of responsibilities or the calls for tender and surveying assig- ic land registry maps. As those data be- nments are as important as the use of known and new surveying technologies. came part of the official cadastral survey, their continuous update is guaranteed.

Data coordination for structural work and railway infra- Aside from data collection, the data ex- F. Ebneter structure. In the sense of a dual-control change between the project participants principle, an external surveying expert (AlpTransit, BAV, SBB, project engineers Tasks and organization of was assigned to assist the surveying pro- from structural work and railway infra- surveying ject management with the technical as- structure, companies, cantonal offices, sessment of concepts and procedures and etc.) represented a great challenge. Using During the first contacts with the project with the examination of inspection re- their usual systems, the different partici- management, we defined the surveying ports. The execution of the survey works pants created documentation in the form tasks. The laying out of the tunnel was for the builder was assigned to external of maps, tables, presentations and re- defined as the main task. Therefore, the surveying companies, mostly to consor- ports. These documentations are packed surveying services were entrusted with tiums. into files and widely distributed. It was our the collection, updating and manage- purpose to exchange them not only in ment of the actual state and project ge- analog but also digital form in order to odata for all the involved parties. The sur- Project fundamentals with guarantee efficient and high quality pro- veying services were also responsible for official cadastral surveying cessing. It was our ideal goal to assure the supervision of the building and of en- that all project participants were able to dangered objects within the range of in- data manage and process these data, among fluence of the project. The collection of the required project fun- them georeferenced data, free of redun- ATG in its function as builder of the new damentals was a special challenge. Dur- dancies, in a GIS. Unfortunately, this was Alpine Rail Tunnel at the Gotthard moni- ing the phase of comparison of rough and not possible at the time due to the large tored the project with a lean organization. detailed variants, actual cadastre data, number of project participants. ATG ar- Numerous engineering companies were land cover data and topographic data on gued that they did not wish to make de- commissioned with the project planning. the Gotthard-Axis between Arth-Goldau mands on the commissioned parties re- It was a far-sighted decision, which can- and Lugano had to be collected in five garding the informatics system they used. not be taken for granted, to integrate a cantons and 50 municipalities. There was Realistically, a heterogeneous CAD/GIS surveying team into the project manage- a great range of possible tunnel routing environment had to be accepted by all ment and to entrust it with the overall di- variants at the time, which did not facili- participants. ATG decided to limit it to a rectorship of the surveying works. The tate the fixing of a perimeter. CAD-performance and made require- tasks and responsibilities were divided be- It was given that the project participants ments concerning only data structure, for- tween constructor services and surveying were to be regularly provided with up- mat and interfaces. A few years later, ATG services of the commissioned contractors dated project fundamentals over a peri- tightened these requirements by intro-

24 AlpTransit Gotthard

Fig. 1: Project variants and the perimeter derived from them for establishing the project basis. ducing the CAD system for the railway in- price for the survey work at the Gotthard above ground network or the main lay- frastructure. and Lötschberg axes in a timely fashion ing out of a whole tunnel on the one hand In agreement with the SBB, the transfer before the beginning of the construction and, on the other hand, many individual of the documentation of the structure to work. This was done in a two-phase se- positions for different expected control the future operator has to be done digi- lection procedure. It was a big challenge and deformation measurements, in order tally and in conformity with the specifi- to describe the required services, the en- to fix the prices. cations of the fixed installations database, vironment context, and the construction the GIS of the SBB. The data coordination site conditions based on the then actual office, as a part of the project manage- project and implementa-tion information Tunnel layout: ment, has proved to be effective. It makes in order to enable the service providers to Requirements for project sure that the continuous project changes propose appropriate concepts and realis- are immediately made available to all partic prices. It was impossible to provide de- engineers and companies ticipants and that all of them can always tailed tender specifications with an ap- In order to attain the requested high qual- access the relevant updated project data. proximately useful quantity framework. It ity of measurements on the complex tun- was nevertheless important to indicate nel building sites, the necessary survey fixed prices for all possible surveying ser- conditions had to be fixed and integrat- Tendering for survey work vices. In this situation, ATG chose com- ed early in the project planning phase as It was important to attract the most effi- prehensive flat-rate positions for the main well as later during the call for tender and cient candidates at the most economical works, such as the implementation of the the assignment of the tunnelling and

25 AlpTransit Gotthard

tion of the existing documentation into the new national survey system was considered too expensive in terms of effort and cost and too error-prone by the project management, it was decided to adapt the network to the old system. During the implementation, it had to be ensured with appropriate measures that the layouts already performed from the net of the old reference system were adapted to the ATG work net. For example, the access gallery to the Sedrun shaft was built using the old national survey system. It was a challenge to communicate these decisions to all project planning and surveying partners.

Control tasks Fig 2: Parts of the contract concluded with the construction companies with We knew from recent experience (Zeuzi- the survey requirements er, Gotthard road tunnel) that the structural work. The big challenge was to in order to make the measurements pos- drainage of groundwater during con- anticipate all possible critical situations sible. struction could lead to settlement on the before they occurred, to get the project surface. The GBT excavation from Sedrun management to agree to the measures Tunnel layout: Primary to Faido runs underneath three dams in derived from them, and to integrate those the critical settlement area. Within the measures in the tender documents and network Position/Height framework of the risk analysis performed contracts with the companies responsible A fundamental condition for the success- by ATG, the possible safety and operation for the structural work. ful laying out of the tunnel is the con- risk of the excavation for the dams was Apart from design and construction mea- struction of a precise and homogenous recognized early on as a significant dan- sures, provisions had to be made for safe- opencast network over the total project ger. One of the key objectives of the pro- ty at work, the date and duration of the perimeter. When this network was im- ject, therefore, was to grant an excava- survey works, acceptable tunnel temper- plemented in 1995, the Federal Office of tion without inadmissible endangerment atures during the surveys, maintaining Topography was busy with the creation of the dams. Accordingly, extensive sur- clear lines of sight, and transport of the of a modern GPS reference net with a new veying and structural measures were in- surveying crews. It was important to con- height reference system, the «New Na- tegrated into the project. firm in the tender all possible services of tional height network LHN95», which re- The surveyors had to permanently identi- the companies relating to the surveys for placed the old national survey system. fy, with a high degree of accuracy, terrain the constructor as completely as possible. ATG wanted to benefit from the high deformations at the surface in the perime- One example of constructive measures quality of the new reference system. At ter of the dams. The surveying concept can be shown at the 800 m long Sedrun the same time, it had to be taken into ac- essentially included the supervision of val- shaft: in the survey concept, an addition- count that all existing ATG project docu- ley cross-sections at the dam walls and al mechanical weight plumbing was mentation was completely referenced to their perimeter; an extensive,100 km long planned over three plumb points at the the old national survey system. It had to leveling line net, both lengthwise and shaft wall, and an optical plumbing in the be decided whether all existing project crosswise to the tunnel axis at the surface middle of the shaft. These plumbings had documents had to be transformed into and in power station galleries, as well as to be possible until the moment of the fi- the new system or whether the network several single points at locations difficult nal breakthrough. For the surveying ac- created on the basis of the new national to access. The extension and degree of tivities in this shaft, which is 8 m in di- survey system had to be integrated into settlement depressions has to be analyzed ameter and crammed with the lift infra- the old reference system. The technical at least once a year on the basis of the structure and all kinds of cables and pipes, feasibility of both variants were analyzed precision levelling and single points. In the plumbing corridors had to be kept open and confirmed. Because the transforma- valley cross-sections, movements of the

26 AlpTransit Gotthard

valley slopes have to be permanently measured with an accuracy of ± 4 mm. The important challenge was to find a surveying company capable of meeting these requirements at an economically advantageous price. At the time of the tendering process (1989/1990), important necessary technologies and Instruments had been developed, but they were still partially in the introductory phase: fully automatic precision tachymeters, GPS-receivers, meteo-sensors, automatic control of measuring processes and data transfer via ISDN/GSM connections, autonomous energy supply, data management and processing software. The harsh climate poses particular requirements to the measuring system. Low temperatures, great amounts of snow with avalanches in win- Fig. 4: Gotthard Base Tunnel routing in the area of the Curnera, Nalps and Sta.Maria dams in the project segment Sedrun – Faido.

ter or strong electrostatic discharges in Technology, the Federal Office of Topog- summer should not be allowed to hinder raphy, the Federal Directorate for Cadas- the measuring system. An ample num- tral Surveying and the cantonal surveying ber of measuring points are unreachable offices contributed significantly to the during 5–6 months in winter. It could not success of the project. The different man- be taken for granted to find a service aging directors of AlpTransit Gotthard AG provider capable of implementing and op- recognized the importance and signifi- erating an adapted measuring system on cance of surveying and respectfully sup- the basis of the given components over a ported the concerns of the surveyors. The period of 20–25 years in this high Alpine other contributions in this publication region. After a minimum of two years of show how many challenges had to be operating the measuring system without tackled and were solved by the different influence from the tunneling, meaningful project participants and how many chal- information could be gained on the «nor- lenges will have to be met until the end mal behavior» of the valley cross-sections. of the project.

Final remarks These and other challenges faced by the surveyors at the GBT could be met thanks to the total engagement, know-how, cre- Franz Ebneter Fig. 3: Transformation variants be- ativity, and great care of all directly or in- Kreuzbuchstrasse 123 tween the Werknetz ATG and the for- directly involved parties. The intensive col- CH-6006 Luzern mer cadastral survey LV03. laboration with the Federal Institutes of [email protected]

27 AlpTransit Gotthard

evaluations, and only a very few special- Surveying the longest railway ists could make use of those possibilities. Professor Fritz Kobold, head of the Insti- tunnel in the world tute of Geodesy and Photogrammetry (IGP) at the ETH Zurich was assigned the The vision of the constructor’s expert task. He entrusted Dipl.-Ing Peter Gerber with the technical management of the The Gotthard Base Tunnel is a great challenge of geodetic engineering. The author project, who carried out his task with has worked more than 20 years as an external expert for the construction manage- great commitment. He created triangula- ment. He thus has first hand knowledge of the needs and processes of such a gigantic tion networks, calculated the achieved ac- project. During the long period from the first studies to the planning to the recent curacies, provided the measuring instru- main tunnelling, countless decisions have been taken, problems have been solved, ments, planned the helicopter assign- and experiences have been acquired. From the perspective of the engineer and the ments and delivered all the required exact professor the author describes the most important stages of the activities, which will coordinates on time. The conducted stud- remain essential for future projects. ies were later summarized in a thesis (1). The political leadership, however, decided for financial reasons to forgo the immediate realization of the tunnel. constructor. It is important to mention in At the same time, Professor Kobold initi- Alessandro Carosio particular that the first surveying work is ated studies on the geoid of Switzerland needed before the consortium and the (probably without being aware of their fu- tunnel construction companies are se- ture importance for the base tunnel) (2). A challenge from all lected. These groundbreaking works were con- perspectives For the Gotthard Base Tunnel, the posi- tinued by his successor, Professor Dr. Max Tunnel surveying constitutes a technical tion of the constructor was first held by Schürer (Professor at the University of and organizational challenge for the con- the SBB. The SBB have an efficient and Bern, lecturer at the ETH Zurich). The re- tractor. The project lasts for several experienced surveying department, sult was an operational computer model decades and thus has organizational re- which had the required competence. The of the geoid for Switzerland, which could quirements. The acquired experience has multiplicity of tasks, but also primarily the be used by any engineering office (3). to be maintained over time. Personnel urgency of the necessary surveying serv- Thus Switzerland was the only country changes and reorganizations are to be ex- ices and studies, necessitated the ap- with a geoid model accessible to all and pected. With the actual dynamics there pointment of an external expert to sup- with an operationally suitable precision has to be agreement to adapt the planned port the SBB specialists. As a newly ap- (Sigma plumb line deviation 0.3 mGon, processes to the technical progress. pointed professor at the Swiss Federal Sigma of geoid height 1 cm locally, 10 cm The surveying services have to be provid- Institute of Technology Zurich (ETH), sur- at the national level). ed for different partners: first for the pro- rounded by competent collaborators, and The professorship for geodesy and geo- ject planning engineers, then for the tun- having a few years of experience in engi- dynamics continued the research under nel construction companies, the railroad neering and national surveying, I was in- the leadership of Professor Dr. Hans-Gert engineers, and finally for the construction terested and was appointed to this task Kahle who took into consideration the as- management for the supervision and doc- in 1991, a position I still hold today. trogeodetic as well as the gravimetric umentation of the project. The surveyors components and improved the instru- have to accept assignments through all mental infrastructure. Thus, a newer and phases of construction and to fulfill them Influences from the past better geoid model became operational quickly and reliably. The construction When the SBB decided to realize the Got- in 1997 (Fig. 1) (4). management has to recognize and sched- thard Base Tunnel project, they commis- The new model was ready in time to be ule all requirements on time, give the ap- sioned the ETH to carry out the basic sur- used for the analyses at the Gotthard tun- propriate instructions, and verify and ap- veys (high precision determination of por- nel. prove the results. It has to commission sur- tals to allow the control needed for the veying specialists as soon as possible (for tunnel work later on). The task bordered My first tasks for the example, a surveying consortium), but it on the impossible at that time. Distance also needs its own specialized profes- measuring instruments were available on- Gotthard Base Tunnel sionals who make decisions, request ser- ly at the ETH. Only the latest computer When I became professor at the IGP in vices and supervise them on behalf of the technologies could deal with complex 1987, I observed that while the newest

28 AlpTransit Gotthard

level accuracy. This enabled me to argue for the importance of further research projects, which my research team started on its own initiative with funding from the ETH. In agreement with my colleagues at the time, F. Chaperon and H. Matthias, I asked to purchase (at DMT in Germany) a high- precision gyro-theodolite as well as research funding for the development and Fig.1: The geoid model of Switzerland. testing of the necessary mathematical models. The ETH had foresight. The vice- developments of modern geodesy were president of serv-ices (C.A. Zehnder) ac- Fig. 2: Student with F. Ebneter, A. Gisi known, the practical experience using this cepted the financing of both projects, and A. Carosio in the safety tunnel of knowledge advantageously in projects thus the ETH was able to perform a num- the Gotthard street tunnel (Airolo was often lacking. At that time, the pur- ber of tests starting in 1992 (Fig. 2). 1992). suit of the Gotthard tunnel project was in As we have at our disposal a climatic discussion, and work on the Eurotunnel chamber that is fully equipped for high- under the Channel was ready to start. For precision direction meas-urements, we young researchers was therefore an indi- regional political reasons local, not par- were able to conduct comprehensive and rect consequence of the expert mission. ticularly experienced, firms were com- realistic instrumental analyses. The most Another important result of the expert as- missioned in France and in Great Britain. im-portant work of this initial period, signment for the Gotthard Base Tunnel Very quickly, technical problems emerged. though, was to study on the effect that was a success-ful series of advanced train- German surveyors were called in to give the irregular gravitational field in the ing seminars on current topics in the field assistance. They succeeded under the giv- Alpine region had on the gyroscopic az- of geodetic engineering (measuring tech- en circumstances. However, the 35 cm er- imuths and on the possibility to correct niques, evaluation methods, geoid, gyro- ror at break-through was more important them mathemati-cally with the available theodolite, etc. [Fig.3]). These were orga- than expected. The reasons for this high geoid model (plumb line deviation). nized in 1993 and 1994 with a view to error were insufficient consideration of re- Further studies concentrated on accuracy future tunnel projects and in which the fraction in the tunnel, disregard of plumb estimates of the planned measurements authors of our research explained the line deviation, and weaknesses in portal under actual condi-tions. This allowed a practical implications of the results. orientation. This situation was known to realistic estimate of the attainable align- There is good reason to believe that the the IGP before the break through at the ment accuracies (5), (6), (7), (8), (9). results of the international tender for sur- Eurotunnel. veying the base tunnel were significantly In 1990, I was given my first mission for influenced by these seminars, which were the Gotthard Base Tunnel. This consisted given several times (Fig. 4). The offers of comparing the newly possible GPS Knowledge transfer from Swiss firms were the most success- measurements with the Kobold triangu- As the Gotthard Base Tunnel project had ful in all respects. They were able to im- lations of the 1970s. This was followed been accepted by the citizens in 1992, the pose themselves in all AlpTransit projects. by investigations concerning the state of major concern was the urgency of trans- The ETH had successfully ensured the technology and the extent of existing sur- ferring technology into practice. This was knowledge transfer and in time had cre- veying data. achieved partially through the participa- ated favorable conditions for the promo- The deficiencies noted at the Channel tion in the research of colleagues or stu- tion of junior surveyors. would have had devastating conse- dents of the department. They were able quences at the Gotthard tunnel. Because to expand their expert knowledge. The of the tunnel length, the orientation had names of the authors of the studies dur- Further research activities to be improved with gyroscopic measure- ing this period can be found in the pub- During the same period, other research ments inside the tunnel, and the neglect- lication index. Most of them later direct- projects were completed, which were of ed irregular plumb line deviations in the ly contributed to the success of the sur- indirect importance for the New Alpine region would have considerably veying works at the Gotthard tunnel as Transalpine Rail Link (NEAT): distorted the gyroscopic true north. Far leaders in the surveying consortium, a) The reliability model for the Swiss na- better evaluation models were needed to where they made use of their expert tional land survey, in practice known as meet the actual requirements for high- knowledge. The successful promotion of «reliability rectangles» (10).

29 AlpTransit Gotthard

published in proceedings and scientific journals.

Verification of surveying work Over time, I was asked to verify a grow- ing number of reports (Fig. 6) containing the results of surveying work. Such controls assured risk minimization. General- ly, no important deficiencies were detect- Fig. 3: Surveying diploma course in Lugano 1994. ed. But the verification offers the opportunity to discuss technical challenges, to b) The methods of robust statistics in ge- After the commissioning, the constructor compare alternatives, and to plan im- odesy (12) (13). transferred the responsibility to the sur- provements. c) The combination of terrestrial mea- veyors of the consortium. Nevertheless, There were a few exceptions. In 1991, an surements and satellite observations in the ETH’s importance for the survey works implementation problem in the geoid planimetric networks (11). at the Gotthard tunnel remained sig-nif- model was identified, which gave differ- These methods are still used in daily prac- icant. ent results depending on the installation. tice today and have become the standard The origin of the problem was corrected proceedings used for the analysis and before it could influence the tunnel rout- evaluation of geodetic measurements at Research on demand ing. In 1998, a problem occurred with the the Gotthard tunnel. They are also used then new high-precision digital levels. at the Lötschberg and Monte-Ceneri tun- Whenever questions arose or there were There were systematic vertical errors in the nels. uncertainties, we started to do research measurements underground. The source to clarify mat-ters. The results were im- of error was identified. The surveying con- mediately documented and put at the dis- sortium from the Lötschberg tunnel de- Operative cooperation posal of AlpTransit Gotthard AG and the veloped a homogenous levelling staff surveyors (for instance, 14, 15, 16, and lighted with LED. The introduction of new The tasks of the geodesy expert have 17). The research work and the results operating rules for these instru-ments al- changed over time. Whereas the focus were relevant on both national and in- lowed the measurements in the base tun- was mostly on scientific research during ternational levels. They were often pre- the first phase, I started to deal with the sented at international congresses and operative part of tunnel surveying in 1994. Together with other experts (F. Ebneter, K. Egger and St. Flury), I was on the editorial committee of the pre-project report, in which the surveying requirements for the Gotthard Base Tunnel were formulated (Fig. 5). The aforementioned ETH-research (simulations, reliability indi- cators, etc.) was applied at this stage. The pre-project report was the basis for the international call for tenders for the surveying works. At the beginning of 1995, I was a member of the evaluation panel that assessed the offers under the leadership of the di- rector of measurements, W. Bregenzer. This led to the commissioning of the surveying consortium VIGBT for the Gotthard Fig. 5: The pre-project report of April Base Tunnel. Fig. 4: The Seminar Program 1994. 1994.

30 AlpTransit Gotthard

nel to be performed in such a way as to cy required today from the beginning of keep systematic influences in the negligi- the project and continuously integrate ble range (Fig. 7). new acquisitions into the planning concept. Unexpected events can require new services or emergency actions. Only a spe- Azimuth measurements cialized entrepreneur able to handle a with the gyro-theodolite wide range of tasks and to provide personnel and competences on demand can During tunnelling, the Institute of Geo- do this. In the case of the Gotthard Base desy and Photogrammetry (IGP) of the ETH Zurich was periodically commissioned to perform gyroscopic measurements in the tunnel (Fig. 8). As the ETH was the only institution in Switzerland to Fig. 7: Systematic errors and levelling. possess a gyro-theodolite with the ability to cali-brate it, such measurements were necessary. sibility. Unexpected events cannot be D. Salvini, who was commissioned by the planned; one can only try to create risk surveying consortium VIGBT, performed scenarios. AlpTransit Geomatik together these works inde-pendent of my analy- with VIGBT and the author did this. For- ses. To provide independent periodical tunately, it has been established that the monitoring, and at the request of AlpTran- planned measures were sufficient to the sit AG and VIGBT, parts of the gyroscop- end. We have been spared emergency sit- ic azimuths were also measured by the in- uations, but it would have been irre- strument manufacturer (DMT Essen) and sponsible not to be prepared for such by the University of the German Federal events. Armed Forces.. Final considerations Fig. 8: The gyro-theodolite of the ETH Zürich in action at the Gotthard tun- The important task of the Surveying a modern tunnel system is not nel. constructor’s expert routine work. It needs competent, experienced and proven geomatics engineers, Tunnel, these conditions were met and In the first phases of the project, the ex- who are able to deal with unexpected fortunately (or maybe thanks to the external expert provides support for the sci- events. A crucial prerequisite for award- pertise of the involved parties) no emer- entific research. He also often has an as- ing contracts in engineering surveying is gency situations or unexpected events oc- sessing function. At all times, but espe- the definition of strict criteria for the ap- curred. The organizational conditions to cially during the performance of work, he plicants, who have to show sufficient ref- succeed even in such an environment has an important safety task in case of an erences from similar works. The candi- were fulfilled. The surveying costs of such emergency. If unexpected events occur on dates also have to guarantee a permanent a project are modest compared to the the technical or organizational levels, he staff, which includes engineers with uni- global costs. High-quality surveying al- and his staff can support or, if necessary, versity degrees and professionals with lows the reduction of the tunnel profile, replace the people with primary respon- technical diplomas in the geodesy field. makes subsequent profile corrections su- Training and experience cannot be impro- perfluous, immediately signals unexpect- vised. It has to be taken into account that ed behavior of the rock, etc. It thereby the surveying services have to be provid- generates substantial economies, which ed over several decades, and that during can easily amount to between 100 mil- that time staff members who reach the lion and 1 billion Swiss Francs; even the age of retirement or opt for career actual amount cannot be proved. It is changes will be replaced. The chosen firm therefore worthwhile to invest sufficient- has to guarantee that competence conti- ly in surveying works in order to minimize nuity is ensured in all circumstances. the risks in this area. The leading personnel must guarantee At the Gotthard Base Tunnel, this policy Fig. 6: Ongoing expertises. the tunnel boring machine (TBM) accura- has proven its worth.

31 AlpTransit Gotthard

Bibliography: (8) O. Reis, Die Überprüfung des Gotthard- (15) A. Carosio, O. Reis, Geodetic Methods basisnetzes, IGP Bericht 224, ETH Zürich (1) Peter Gerber, Das Durchschlagsnetz zur and Mathematical Models for the Estab- 1993, www.igp-data.ethz.ch/berichte/ Gotthardbasislinie, Doktorarbeit ETH Zü- lishment of New Trans-Alpine Transpor- Graue_Berichte_PDF/224.pdf. rich 1974. tation Routes, IGP Bericht 260, ETH Zü- rich 1996, www.igp-data.ethz.ch/berich- (2) Alois Elmiger, Studien über die Berech- (9) O. Reis, Calculs de simulation pour la li- te/Graue_Berichte_PDF/260.pdf. nung von Lotabweichungen aus Massen, gne de base du St. Gothard, IGP Bericht Interpolation von Lotabweichungen und 231, ETH Zürich 1994, www.igp-data. (16) Desiderio, R. Koch, Der Einfluss der Tem- Geoidbestimmung in der Schweiz, Dok- ethz.ch/berichte/Graue_Berichte_PDF/ peratur auf Kreiselazimute hoher Präzisi- torarbeit ETH Zürich 1969. 231.pdf.. on, IGP Bericht 281, ETH Zürich 1998, www.igp-data.ethz.ch/berichte/Graue_ (3) Werner Gurtner: Das Geoid in der (10) A. Carosio Hsg, Zuverlässigkeit in der Ver- Berichte_PDF/281.pdf. Schweiz, Doktorarbeit ETH Zürich 1978, messung, Weiterbildungstagung ETH- www.igp-data.ethz.ch/berichte/Blaue_ Hönggerberg 15. und 16. März 1990, (17) Dante Salvini, Deformationsanalyse im Berichte_PDF/20.pdf. www.igp-data.ethz.ch/berichte/Graue_ Gotthardgebiet, IGP Bericht 297, ETH Zü- rich 2002, www.igp-data.ethz.ch/berich- (4) Urs Marti, Integrierte Geoidbestimmung Berichte_PDF/169.pdf. te/Graue_Berichte_PDF/297.pdf in der Schweiz, Doktorarbeit ETHZ 1997, (11) A. Carosio La combinaison de mesures http://e-collection.ethbib.ethz.ch/ terrestres et par satellite dans les réseaux eserv/eth:40540/eth-40540-01.pdf. planimétriques, Vermessung, Photo- (5) M. Zanini Hochpräzise Azimutbestim- grammetrie, Kulturtechnik 10/1992, mung mit Vermessungskreiseln, IGP Be- www.igp-data.ethz.ch/berichte/Graue_ richt 209, ETH Zürich 1992, www.igp-da- Berichte_PDF/311.pdf. (Siehe Kap. 14.) ta.ethz.ch/berichte/Graue_Berichte_PDF (12) Fridolin Wicki, Robuste Ausgleichung /209.pdf. geodätischer Netze, IGP Bericht 189, ETH (6) K. Maser, Alptransit, Portalnetz Polmen- Zürich 1992, www.igp-data.ethz.ch/be- go. Absteckung des Portals des Sondier- richte/Graue_Berichte_PDF/189.pdf. stollens zur Untersuchung der Pioramul- Prof. Dr. Alessandro Carosio de IGP Bericht 213, ETH Zürich 1993, (13) Fridolin Wicki, M-Schätzer, IGP Bericht em. Prof. für Geoinformationssysteme www.igp-data.ethz.ch/berichte/Graue_ 190, ETH Zürich 1992, www.igp-data. und Fehlertheorie Berichte_PDF/213.pdf. ethz.ch/berichte/Graue_Berichte_PDF/ 190.pdf. Institut für Geodäsie und (7) M. Zanini, R. Stengele, M. Plazibat, Krei- Photogrammetrie selazimute in Tunnelnetzen unter Einfluss (14) O. Reis Mesures gyroscopiques et dévia- des Erdschwerefeldes, IGP Bericht 214, tion de la verticale, IGP Bericht 249, ETH ETH-Hönggerberg ETH Zürich 1993, www.igp-data.ethz.ch/ Zürich 1995, www.igp-data.ethz.ch/be- CH-8093 Zürich berichte/Graue_Berichte_PDF/214.pdf. richte/Graue_Berichte_PDF/249.pdf. [email protected]

32 AlpTransit Gotthard

a steering system from the VMT Compa- Gotthard Base Tunnel survey ny. Both machines had their starting point in the mountain: east by TM 2500; west challenge from a contactor’s by TM 1500. Before drilling started a tunnel network was measured in each tun- point of view nel to provide the TBMs with a Tunnel Guidance System. The net points are In January 2002 the survey section from the TAT joint venture started work on the Bo- brackets based on height in the middle of dio – Faido and Faido – Sedrun phases. All survey documents were handed over to the tunnel and one metre from the site. the contractor from the client. In the beginning it was a one-man show, but soon mo- So there was nearly no refraction, which re surveyors had to be employed. Because both phases were running at the same ti- was shown by calculation of the network. me, the joint venture decided to give the survey work for drilling and blasting in Fai- Network measurements were done after do for the multifunction station (MFS) to a subcontractor called Amberg Technolo- every 150 m advance with an overlap of gies. Amberg Technologies also did all of the geotechnical measurements. The the old net. Included were the stake-out mechanical advance, interior construction, and surveying for the bypasses for both points on the floor and the points for phases, were incurred by the joint venture survey. steering. Inside the TBM we measured two polygons, one in the lane of the laser and one in the range of the floor. The polygons were connected to the network. In front of the TBM the polygons were points, the first TBM started in November brought together so that we had the same R. Deicke 2002 in the east tunnel and the west TBM system for advance and stake out of the in March 2003. Both TBMs are guided by concrete parts. The first project was to stake out the installation area and make the necessary preparations for drilling and blasting in Faido. The drilling and blasting heading was steered by a motor laser using the programmes TMS-Office and TMS-Set out. In the meantime, ten areas were being worked on at the same time. Once the survey data were loaded into the jum- bo drill, the blasting holes could be drilled automatically. In the MFS the rock was very active and several cave-ins occurred, which had to be controlled, and intensive deformation measurements were taken in 3D with the involvement of extensome- ter, inclinometer, and tape. Capsule pressure and strain gauge made the survey- or’s life difficult. New checks conducted again and again for the main measure points didn’t allow the surveyors much rest. The drilling advanced over 24 hours a day, 7 days a week. Together with work in the tunnel, everything else had to be calculated and documented. After long working days over 4½ years, the drilling and blasting work was finished; ~9.500 m of different tunnels were dug. After the tunnel boring machines (TBM) were recalibrated by the fabricator Her- renknecht and provided with control Fig. 1: Motor laser with measures for the tunnel ring construction.

33 AlpTransit Gotthard

sealed, we scanned the tunnels. With these data we checked the planarity of the shotcrete, which is an important element for sealing. With the same data we produced cross-sections for planning interior construction. From the set of drawings we identified the joints for the formwork. After construction of the lined tunnel we mounted station plaques and checked the tunnel once more with cross-sections. Final- ly, we staked out the banquettes whereby the structural work was finish. The tunnels were scanned again to verify the clearance diagram and to see whether there were cracks inside the concrete. If the cracks are too big, they have to be re- furbished with concrete. At the same time there were set out and control measurements in Faido MFS. In- volved were concrete work in the four tee- Fig. 2: Illustration of the holes to be drilled. junctions, connection tunnels, exhaust tunnels, and side tunnels. Along with nearly weekly network mea- The measurements of the main points surements in both tunnels, as well as sup- from the contractor were checked by the port for tunnel guidance systems, and client every 500–800 m. The differences transact laser station there was work for over the years were only a few millimetres. steering the crosscuts. Added to this we Over the decade, teams put in 9 days work constantly measured cross-sections in the with 5 days off. At peak periods, we areas that were in motion and in all cross- worked with 18 people in our section; to- cuts. Before the drilled tunnels were day we are down to 9.

Fig. 3: Different mounting parts for deformation measurements.

Fig. 4: Tunnel boring machine at the Herrenknecht plant Fig. 5: Components of the guidance system.

34 AlpTransit Gotthard

Fig. 6: Network configuration. Fig. 7: Measurement console with footing platform.

Fig. 8: Construction of the tunnel bench. Fig. 9: Concreted, completed tunnel.

The break through in the east tunnel was tion contractor our break through results Reinhard Deicke on 15.10.2010 and so the east tunnel is are 8 cm laterally, 0 cm in height, and 14 Consorzio TAT non-stop from Bodio to Erstfeld – 57 km. cm in length. Isengrundstrasse 18 With good cooperation between client, CH-8134 Adliswil Amberg Technologies, and the survey sec- Good luck together. [email protected]

35 AlpTransit Gotthard

marking the key machine measurement Navigation of the tunnel- points. Additionally geometric machine data (including Ram extensions) from the boring machine at Gotthard TBM’s PLC were stored and used in the calculation of the actual position. Special requirements for the construction of the tunnel drives on the Gotthard Base Concurrent with the advance, various Tunnel meant high demands on the navigation systems of the four TBMs. Due to the other works needed to be done: initial necessity of tunnel works to be carried out concurrently with the advance, various fac- shotcreting, wire mesh and arch-mount- tors, such as line of sight dust, heat, and vibrations, prevented a normal measuring ing, and rock bolt boring, which serious- operation. This article shows how VMT produced secure navigation of the TBMs, ly interfered with the line of sight to the through the selection of suitable material and a change of measuring methods. machine measurement points. Therefore a standard measuring method couldn’t be applied. Extreme vibrations will affect all these hardware components, from total stations and computers up to the shuttered prisms.

Navigation System in the M. Messing Requests on the Guidance System Gotthard-North – Amsteg A guidance system is equivalent to a nav- Section Guidance of a tunnel-boring machine igation system. It provides information to In the North Section the first three trail- (TBM) is comparable to navigating a su- start a control or course correction. There- ers were continuously pulled over rails per-tanker: it takes a long time before the fore it is indispensible that the actual po- during the advance. The following trailer effect of a course-correction is obvious. sition of the TBM in relation to the units were hanging on roller-brackets on Skilled machine drivers know how «their» planned tunnel axis is continuously pro- the segment and were pulled only after machine performs in different geological vided and displayed. As a 98% availabil- the advance (see Fig. 1). So this area was conditions. Therefore, a precise and reli- ity of the TBM position is required, con- stable for a short time and could be used able determination of the TBM’s position tinuous measurement of the TBM posi- for measuring the cutter head, however, is the most important information for tion is necessary. Additionally, the pitch only in the lower laser window. The co- steering control. Although the TBM and roll values of the TBM must be col- ordinates and orientation for the auto- moves slowly, it is possible for the ma- lected and displayed. A status indication matic total station in the lower section chine to stray off the planned course and of all relevant sensor components of the had to be determined again after each ad- exceed the requested precision of 100 guidance system is required as well as au- vance. In this section it was done by con- mm round the given axis. It is a real chal- tomated direction control. tinuously carrying forward key machine lenge to eliminate these deviations in such Normally, the well-known navigation sys- measuring points in the invert area. For a long tunnel,, and can only be achieved tems work with GPS. But in a tunnel there measuring the tracks on which the first with perfect coordination between sur- is no satellite reception. So the determi- trailer section was pulled forward, these veying and machine driving. A polygonal nation of position is carried out in the clas- points had to be pegged out anyway. They process from outside the tunnel right up sic mode with the help of motorized mea- were also used for automatic measuring to the machine’s cutter head must carry suring instruments. of a «free chainage» of the total station all geodetic information. Normally for this (see Fig. 2). purpose, in the machine area, along the Characteristic of Gotthard After each advance this trailer area was tunnel wall, there is a dedicated clear area pulled forward, whereby the coordinates or laser window available throughout the System and the orientation of the total station entire area of the trailing gear. One spe- For the Gotthard tunnels two different changed. After the grippers were en- cial characteristic of the Gotthard project trailer concepts were in use for the north gaged again, a signal was sent to the con- was that various tunnelling activities and south sectors. To cope with these cir- trol computer that started the automatic needed to be done concurrently with the cumstances different navigation systems measuring of the total station with the advance, thus the machine and trailer had to be designed using the same hard- present key machine measurement concept was designed accordingly. The ware components, including motorized points. If the coordinates and the orien- navigation system had to be adapted to total stations, inclinometer, and also the tation of the total station were known, this situation too. software controlled shuttered prisms the TBM position could be measured by

36 AlpTransit Gotthard

mounted on a divert frame which was Mobile trail during advance connected to the frontal walking mechanism and independent from the trailer (see Fig. 6). During the advance this mechanism did not move. It was only pulled forward after the advance. With the short time, stable machine station the motorized prisms were measured and the glob-

During advance al coordinates calculated during the mea- Tracks Maschine prism short time stable surement cycle. Then the TBM’s position Machine Total station was determined by a special transforma- 2 axis iclinometer on AD12 tion (see Fig. 7). As the TBM stays in ad- Fig. 1: Trailer concept Gotthard-North section. vance mode within these measuring cycles, a track correction is added to the the automatic machine prism at the cut- the machine axis. This «local» co-ordinate measurements of the motor prisms (dy- ter head (see Fig. 3). The total station was system was incorporated into the com- namic transformation). mounted on a self-levelling tribrach (AD- puter calculations. During the advance As with the Gotthard-North system the 12), which compensated for any roll and the machine framework moved forward. coordinates and orientation of the ma- pitch of the trailer and automatically lev- The machine station (motorized total sta- chine station were stable only for a short elled the total station. tion on an automatic tribrach AD-12) was time. This means they changed with each

Navigation System in Concrete spraying works Gripper the Gotthard South – Maschine station Concrete spraying works Bodio Section

In the southern section the trailer was ad- Trailer vanced using the two walking mechanisms, which were deployed during the Stepper advance. After the advance these mech- Cutter head Motor prism anisms were contracted and the trailer moved ahead. Here the walking mechanisms could be assumed to be a short Wall mounted station Trailer Alignment target time, stable construction (see Fig. 4). Four motorized shuttered prisms (machine prisms) were mounted on the machine frame (see Fig. 5) and measured on Fig. 4: Trailer concept Gotthard-South section.

Fig. 2: Total station Gotthard-North. Fig. 3: Installed shuttered prisms (closed).

37 AlpTransit Gotthard

Fig. 5: Shuttered prisms on machine frame. Fig. 6: Divert frame with machine station. advance. When an advance was made, driving process should in no way be af- fore, sincere thanks are given to all par- the grippers were contracted, moved for- fected. Several times during the advance ties involved, for their patience and un- ward, and then extended again on the not only were geometric system adapta- derstanding during the set up of the sys- tunnel wall. A signal was then given by tions necessary but also changes in some tem and the necessary revision phases. the TBM to the control computer, which hardware components. For example, the All things considered, this project has con- started measuring the machine station controller unit (data conversion and net- tributed to many enhancements of tech- from the wall-station mounted in the rear. work) had to be cooled with compressed nique and methods from which many fu- The measuring operation took about two air and had to conform to at least the IP62 ture projects will benefit. minutes. Afterwards the shotcrete work protection category. in the backup area could continue. The use of similar hardware components VMT GmbH Gesellschaft für and a modular software system was ben- Vermessungstechnik eficial as all the necessary adaptations Stegwiesenstrasse 24 Display of TBM Position could be done with relatively little effort. DE-76646 Bruchsal On the monitor (see Fig. 7) all relevant Things didn’t always flow smoothly, there- [email protected] control data are displayed for the machine driver. Aside from the deviations of the planned axis (horizontal and vertical), the roll and pitch are also shown. The indication of the operating state of the connected sensor system is displayed as well as the station and the advance number. From this display the direction control and also the display of the last (historical) shield drive could be activated. The latter provides information on the performance of the TBM, which directly influences the control.

Abstract Adapting the navigation system to the special drive-operations was doubtless a big technical challenge. The components and materials used were subject to very problematic conditions, such as vibration, dust and heat. The operating mode of the navigation system had to be fully orien- Fig. 7: TBM position in relation to the planned tunnel axis, calculated by trans- tated to these tunnelling operations as the formation.

38 AlpTransit Gotthard

ic deflections of the vertical, but is addi- National Surveying tionally enhanced by GPS observations on control points of the national vertical net- contributions to the AlpTransit work and by gravimetric data. The increased accuracy is mainly a result of the Gotthard Base Tunnel many additional measurements, but also due to the improved height and mass During the 1990s the Federal Office of Topography, swisstopo, designed the new LV95 models. In order to guarantee the consis- national geodetic survey of Switzerland and launched its principle element, the na- tency between the ellipsoidal heights of tional GPS network. The LHN95 national vertical network and the computation of a the GPS network (LV95), the orthometric new geoid model of Switzerland completed the new national surveying network. heights of the LHN95 as well as the geoid Thanks to its homogeneous accuracy of a centimetre for all of Switzerland, it also sa- undulations of the new geoid model, their tisfies the basic surveying requirements for large engineering projects such as the Gott- measurements and data were combined hard and the Lötschberg base tunnels. . and adjusted in the so-called «Swiss Com- bined Geodetic Network (CHCGN)».

Preliminary project points, carried out the surveying work, A. Wiget, U. Marti and A. Schlatter and measured connections to interna- Gotthard Base Tunnel tional reference networks. Together with From the very beginning, the Federal Of- The National Surveying Network 1995 the GNSS permanent network AGNES, fice of Topography's ambition for LV95 – The geodetic survey of Switzerland is one these points are the realization of the new besides meeting the requirements for the of the main activities of the Federal Of- reference frame for the LV95 national sur- official cadastral survey in Switzerland – fice of Topography, swisstopo. It com- vey network, which practically replaces was to fulfill the demands of large engi- prises the production, development, and the LV1903 national triangulation net- neering projects and to create synergies maintenance of the basic geodetic works work (1st to 3rd order). Comparative sur- for the demanding nature of engineering such as the terrestrial reference system veys showed distortions of up to 1.5 m surveys [Schneider et al. 1996]. In research and its realization through so-called ref- (in some areas systematic) in the 100-year- projects initiated by the Swiss Geodetic erence frames using geodetic control net- old LV03. In contrast, the nation-wide ac- Commission (SGC), swisstopo quickly works and permanent networks. Begin- curacy (1 sigma) of the position coordi- gained a leading position in GPS applica- ning in the mid-1980s, it was possible to nates of the LV95 reference frame is bet- tions for engineering surveys thanks to overhaul the national survey at reduced ter than 1 cm. The new national survey early practical applications from satellite costs using the modern technologies of has therefore improved the accuracy in geodesy (GPS) in the national survey and satellite geodesy, in particular GPS, there- position by a factor of 100. the close collaboration with the Astro- by significantly improving its accuracy and The new LHN95 national vertical network nomical Institute at the University of Bern applicability. swisstopo renewed the na- is still based on the first-order levelling (AIUB) and the Institute for Geodesy and tional geodetic survey within the scope of network. For the complete revision of all Photogrammetry (IGP) at the Federal In- the «New National Survey LV95» project levelling data since 1903, the spatial vari- stitute of Technology in Zürich (ETHZ). [Signer 2002]. The most important com- ations of the earth's gravity field or the Furthermore, swisstopo had acquired ponents of the LV95 are: the definition of equipotential surfaces (geoid model) as long-term experience in triangulation the geodetic reference systems CHTRS95 well as the tectonic movements of the measurements, in large-scale precision and CH1903+, the fundamental station control points (kinematics of the earth's levelling and gravity field determinations Zimmerwald, the national GPS network, upper crust) are modelled and subjected as well as in deformation observations the Automated GNSS Network Switzer- to a kinematic adjustment. As opposed to and in the necessary know-how to opti- land (AGNES), the positioning service the official heights of the LN02 leveling mally combine these measurements. By swipos, the national vertical network network, the heights from the LHN95 are the end of the 1980s swisstopo was en- LHN95, the national gravity network computed and adjusted as theoretically gaged in different basic surveying activi- LSN2004, the geoid model of Switzerland rigorous orthometric heights above the ties for large engineering projects, espe- CHGeo2004, and the kinematic model geoid. cially tunnel surveys for RAIL2000. CHKM95. Therefore, the new national surveying The coordinating group «AlpTransit Sur- Between 1989 and 1995, swisstopo de- network also includes a new geoid mod- vey», including representatives from con- veloped the GPS network with over 200 el (CHGeo2004) which – like the former tractors (SBB and BLS) and experts from stable and permanently monumented one – is primarily based on astrogeodet- federal surveying authorities and from the

39 AlpTransit Gotthard

ETHZ, was created in order to coordinate ence frame (see above) that also allowed the basic surveying tasks for AlpTransit the accurate correlation to global refer- with the national survey and the official ence systems applied in satellite geodesy. cadastral survey. On behalf of this group, The constraints in the existing survey net- various problems encountered in the pre- works were detected through the ob- liminary project were remedied by the IGP served relationships to the 1st and 2nd as well as by swisstopo. These studies order triangulation network and the 1st served as a basis for the public tender for order levelling network. In coordination the surveying work. with the concept and observation of the In order to reach the high accuracy re- fundamental GBT network and the «Gott - quired for large tunnel networks, partic- hard Süd» (Bodio – Lugano) section to the ularly in the Alps, geodetic characteristics south, swisstopo established and ob- such as spatial variations of the gravity served additional LV95 control points in field, the kinematics of the earth's upper 1995. Thus, there were a total of eight crust, and the influences on GPS obser- LV95 points available for the fundamen- vations caused by refraction need to be tal AlpTransit network: Altdorf, Amsteg, taken into account. swisstopo was able Oberalp, Disentis, Dalpe, Biasca, Bel - to incorporate different experiences linzona and Sonvico. The first six were gained from the national GPS network used for the GBT, and the latter three for and the levelling network into the Got- the «Gotthard Süd» section. thard Base Tunnel (GBT) project. In addi- The concept of the fundamental network tion, there were findings that were not was designed to establish the connection directly related to the cut-through, but to the new LV95 national surveying net- nevertheless had to be taken into consid- work using these reference points. On the eration for the overall project, i.e., the other hand, in each portal and for each Fig. 1: Partial network LV95 showing st subsidence above the Gotthard road tun- intermediate access shaft local triangula- the 1 order leveling lines (LHN), grav- nel determined through levelling (see Fig. tion points were included in the observa- ity and astrogeodetic points used in 6), which lead to a monitoring concept tions to allow connections to the LV03 na- the fundamental survey of the Got- for the dams above the GBT during tun- tional survey and to the cadastral survey. thard Base Tunnel. nelling In May 1996, the coordinating group «AlpTransit Survey» made the preliminary ing of the network. A comparison to the decision (subject to further investigations) coordinates of the LV95 national GPS net- Horizontal reference frame to carry out the survey work for AlpTran- work showed maximum differences Even in the mid-1970s the recommend- sit primarily in the LV95 reference frame. (residuals of a Helmert transformation) of ed aboveground survey for the GBT was In close cooperation with the SBB and 5 mm [Haag et al. 1996]. A repeat mea- a combined triangulation network with Canton Uri, and in combination with the surement in 2005 resulted in similar dif- directional and distance measurements cadastral surveying project RAV Subito, ferences of up to 2–6 mm [Schätti and Ryf [Gerber 1974]. Twenty years later a high- swisstopo carried out tests in 1996 in the 2007]. The LV95 points contributed not precision GPS network combined with Reuss plain from Altdorf to Amsteg to only to the greater accuracy of the fun- conventionally observed portal networks transform spatial data from LV03 to LV95, damental network but also accounted for (directions, distances, elevation angles) and to obtain the optimal triangular trans- a significant improvement in its reliability, was indisputable. The portal networks, for formation network for the FINELTRA a vital component of tunnel surveying. which additional astronomic azimuths transformation method. and vertical directions were measured, The GPS observations for sections «Gott - Positioning in LV03 were used to transfer the positioning, the hard-Basistunnel» and «Gotthard Süd» The result of the combined adjustment of scale and the orientation of the above- were each carried out by the consortium GPS observations and conventional mea- ground network into the mountain with Gotthard Base Tunnel Survey (VI-GBT) and surements was a set of highly precise co- the least possible loss of accuracy. the Consorzio Geodetico Sud (COGE- ordinates with an internal accuracy in cen- SUD), during two days in November 1995 timetres. This now had to be positioned Fundamental GPS network and January 1996, respectively. The LV95 in a well-defined reference frame. At the With the LV95 national GPS network, in points were occupied permanently for the request of the two consortia and based the mid-1990s swisstopo had provided a entire duration of the measurements in on a new evaluation of the «AlpTransit modern, high precision, geodetic refer- order to guarantee an optimal position- Survey» coordinating group, in 1997 the

40 AlpTransit Gotthard

This model is not just a simple reference surface for height determination, but also an actual 3-D model, which also allows the interpolation of gravity values and deflections of the vertical on arbitrary points within and outside the earth's surface. In 2004, CHGeo98 was replaced by the more sophisticated CHGeo2004, which is based more closely on GPS/levelling, but at the same time still on vertical deflections and in addition on gravity measurements. But the CHGeo98 model was used in the entire construction of the GBT until its completion. Initially, it was not yet clear if the quality of the CHGeo98 would be sufficient to meet the required tolerances in the con- Fig. 2: LV95 station Biasca. struction and breakthrough of the GBT. Therefore, additional measurements and AlpTransit project management reached sions due to parallelism of LV95 and investigations were carried out. One of its definitive decision to carry out the GBT LV03). the studies [Marti 2002] was designed to survey in the «NetzGBT Lage» local net- It should be mentioned at this point that answer the question whether for the GBT work. Even though the NetzGBT network, a different positioning reference frame a more sophisticated mass model, instead with 31 points, and the one for the «Gott - was chosen for the survey of the BLS Alp- of the CHGeo98, would yield the accura- hard Süd» section, with 21 points, relied Transit Lötschberg Base Tunnel: it was sur- cy required for deflections of the vertical on the highly accurate LV95 network, they veyed entirely in the new LV95 reference and for the orthometric correction. Since were both positioned in the LV03 refer- frame [Riesen et al. 2005]. These two so- the CHGeo98 was based only on surface ence frame through transformations to lutions show that both alternatives can be observations and the mass model was minimize the misclosures around the por- carried out successfully, provided that the fairly rudimentary, it was uncertain tals and the access tunnels. The con- choice of frames is implemented consis- whether this model would pose problems straints in LV03 between Altdorf and tently. in the construction of the tunnel. Conse- Lugano, however, called for two different quently, a local three-dimensional mass transformations for the GBT and section model was generated from the available «Gotthard Süd», respectively, which dif- Gravity field geological profiles to determine its influ- fered primarily by a 10 ppm discrepancy The earth's gravity field influences practi- ence on deflections of the vertical, the in scale. The reasons for this choice of ref- cally all geodetic observations and must gravity and the orthometric correction. erence frame and the rejection of the therefore always be taken into consider- Comparisons to the standard CHGeo98 technically ideal case (suggested by swis- ation in a large project such as the GBT. model showed differences up to 0.5 stopo) of constraint-free positioning in This includes correcting ellipsoidal heights mgon for the deflections of the vertical LV95 were: determined with GPS by the geoidal that occur mainly along the edges of ge- • preliminary activities for AlpTransit had height, positioning the network by means ological layers featuring large contrasts in already been carried out in LV03 of astronomic azimuths, correcting ter- density. This amount lies within the toler- • rail surveys of the existing SBB lines restrial measurements (especially gyro- ance of significance for the correction of (Database DfA, rail plants, track geom- scopic measurements) by the influence of gyroscope measurements, thus it was de- etry) were available in LV03 the deflection of the vertical, and cor- cided to use the standard model. On the • cadastral surveys of the involved mu- recting levelled heights by the influence other hand, gyroscope measurements nicipalities were in LV03; decisions for of gravity (orthometric correction, see the should not be carried out directly in geo- converting to LV95 in cadastral survey- following sections). logical transition zones. Gravity correc- ing were pending When construction of the GBT began, the tions obtained from the mass model pro- • massive cost increases were anticipated standard geoid model was the CHGeo98, duced differences of approx. 6 mGal com- for the conversion which is essentially based on measure- pared to those from the CHGeo98. • collaboration with external partners ments of the deflection of the vertical and However, the influence on the orthome- would have been more difficult (confu- also on GPS/levelling data [Marti, 1997]. tric corrections was only 2 mm at the

41 AlpTransit Gotthard

As for the gravity measurements, it was also necessary to verify whether the values computed from the CHGeo98 were sufficient for the deflections of the vertical and the astronomic azimuths, or if additional observations were required. In summer 2005, the ETH Zurich together with the Technical University of Hannover carried out astrogeodetic measurements around the portals and in further access tunnels. These measurements are documented in another article in this volume [Bürki, Guillaume]. The main result again Fig. 4: Gravity measurements in the showed that the values interpolated from tunnel. the CHGeo98 were adequate for the construction of the GBT and no further ob- based on measurements from 1st and 2nd servations would be necessary. order levelling (substantially even on the The various investigations of the gravity lines from 1970–73 mentioned in Gerber field confirmed that the CHGeo98 geoid [1974]) as well as on computations of the model of the national survey was already new vertical network LHN95. For the sufficient for large projects such as the breakthrough of the 57-km-long tunnel, GBT, and additional costs for further ob- only approx. 30 km of additional above- servations could be avoided. The subse- ground precision leveling was required. Fig. 3: Geoid model CHGeo98. quent CHGeo2004 delivered further im- These were used to connect the portals provements, especially for the consisten- Erstfeld, Amsteg, Sedrun, Polmengo (Fai- most, which meant that the standard cy of height determination with GPS and do) and Bodio (Biasca) to stable points in model with its uniform density was also levelling. the LHN vertical network. All subsequent sufficient. This investigation established observations to the extent of several hun- that the CHGeo98 mass models were ad- Fundamental vertical dred kilometres were requested for sub- equate for constructing the GBT and sidence monitoring, supplements to the denser models were not necessary. On the network portal networks and tectonic investiga- other hand, the evaluation did not answer Levelling as main component tions. They had no direct bearing on the the question whether gravity measure- In the final report of the «Gerber net- breakthrough. ments should be made inside the tunnel, work», the first fundamental network of or whether the extrapolated values from a projected Gotthard base tunnel, there Heights in the Alps the surface would suffice for the height was only the following mention concern- Whereas height determination by means correction. ing the height: of levelling is a well-known and simple For clarification, gravity measurements The heights of the two portals and the method, the handling of heights in geo- were carried out in 2005, in collaboration three access tunnels were determined desy is regarded rather as an academical- with the Institute for Geophysics at the through levelling by the Federal Office of ly complicated (and annoying) necessity. University of Lausanne, on a few points Topography… at this point it would sure- A levelling loop «pass road – vertical ac- around the portals and in the already ac- ly be futile to make further mention of cess shaft – rail tunnel», however, fea- cessible part of the tunnel and compared the high accuracy of the already legendary tures special characteristics. For the ex- to values interpolated from the CHGeo98. and internationally acclaimed work at the perts, this means: the usual levelling The resulting differences of less than 3 Office of Topography with its keen sense heights obtained along the pass road are mGal were negligible for determining or- of tradition [Gerber 1974]. neither fish nor fowl, vertical access shafts thometric corrections. It was therefore de- Basically, the first sentence also applies to yield orthometric height differences, and cided not to carry out systematic gravity the GBT. The following paragraphs, how- in tunnels with a gentle incline the heights observations in the GBT and that the ever, should demonstrate that for a pro- are almost exactly dynamic ones. Using CHGeo98 yielded sufficiently accurate ject of such dimensions, further concepts, the GBT as an example for the layperson: gravity values. The investigation is docu- observations and computations would be if no corrections are applied with respect mented in swisstopo Report 05–34 [Bür- required instead of complacent praise. to the gravity field, the misclosure of even ki et al. 2005]. In fact, the vertical network of the GBT is error-free levelling loops is around a

42 AlpTransit Gotthard

decimetre. Together with the inevitable tential differences) together with the in- counteracted, then corrections have to be random errors in measuring, there isn't fluence of the mean gravity along the applied to the height transitions during much leeway for attaining the required plumb line, which cannot be computed the tunnelling stages, in particular: breakthrough tolerance of 12.5 cm (2. free of hypotheses. • influence of the gravity field in the tun- 5σ). Tab. 1 shows the differences between nel (orthometric corrections and theo- LHN95 and the official LN02 heights as retical loop misclosures, respectively) LHN95 as a basis well as the computed vertical velocities • influence of the differences between The idea of having the fundamental relative to the Erstfeld portal. In addition, LHN95 and LN02 (see Tab. 1) heights based on the (at that time) pro- the difference of the results of a kinematic • influence of the different uplift rates jected new adjustment of the LHN was adjustment carried out on pure levelling (see Tab. 1), which should theoretically founded on an agreement between swis- differences to LN02 can be seen in col- remain only slightly over 1 cm for the stopo and the VI-GBT [Schneider and umn «LNIV–LN02». entire period of construction (10 to 20 Haag 1995]. It is closely tied to the real- years). ization of the new LV95 national survey LN02 as frame for project heights and in particular the new LHN95 vertical The reason why the difference between Orthometric corrections network [Schlatter and Marti 2007]. The the official heights (LN02) and the ortho- Even if the surveying of the tunnel had same concept was also implemented suc- metric heights (LHN95) amount to been started with portal heights in cessfully in the construction of the decimetres was presented in Schlatter and LHN95, the tunnel levellings would have Lötschberg base tunnel [Riesen et al. Marti [2005]. The most important causes had to be corrected by the influences of 2005]. in LN02 are summarized as follows: gravity or at least by the expected loop LHN95 is based on an orthometric height • the influences of the gravity field (or dif- misclosure. Based on the available height system and was realized through a kine- ferent types of heights) were not taken and density models – such as they had matic new adjustment of all measure- into account been used for determining the geoid – ments made since 1903. In addition to ad- • precise levelling observations are still swisstopo computed for the VI-GBT a pri- justing the influences of gravity, the tec- constrained into nodal points whose ori orthometric corrections using project tonic movements (alpine uplift of up to heights are based on the 'Nivellement coordinates. The process is shown in Fig. 1.5 mm/year) are also taken into consid- de Précision' from 1864-91 5 with the example of the breakthrough eration. • the known recent vertical changes had Amsteg ǟǞ Sedrun north. It is striking The following advantages, besides mini- not been included. that the vertical shaft did not have any di- mal expense and effort for new observa- Nevertheless, the project management rect influence; the vertical distance corre- tions, are relevant for the construction of and the VI-GBT decided to stay with LN02 sponds so to speak to an orthometric the GBT: since the project as well as connecting height difference. The breakthrough er- • high precision and improved reliability constructions had already been observed ror, which would have resulted from hav- • elimination of the influence of errors in this frame [Haag and Stengele 1999]. ing ignored the loop misclosures, never- caused by the gravity field at the break- The realization of the Lötschberg base theless amounts to approx. 3.8 cm. through tunnel where LHN95 was used as the • elimination of the influence of errors working frame proved that it also works Comments and conclusion caused by measurements from different the other way around. If the disadvan- In retrospect it is remarkable and to the epochs tages and shortcomings of LN02 are to be merit of those responsible at the time that • compatibility of ellipsoidal heights from GPS observations and from the Height Length GBT m. F. LHN95 LHN95 - LN02 LNIV - LN02 Uplift CHGeo98 geoid. Portal Orthometric heights and vertical veloci- m a.s.l. [km] [mm; 1σ] [m] [m] [mm/y] ties of the portal points from a prelimi- Erstfeld 460 0 ± 0 (Ref.) 0 (Ref.) 0 (Ref.) 0.67 nary adjustment carried out on the LHN95 in 1999 (comprising approx. 6800 km of Amsteg 510 8 ± 3 0.02 0.01 0.78 a total of 12000 km of levelling lines) were Sedrun 1410 21 ± 9 0.13 0.01 0.80 delivered to the VI-GBT. The relative mean Faido 760 40 ± 7 0.11 0.05 1.25 error (1 σ) as compared to the Erstfeld Biasca 300 57 ± 8 0.11 0.09 1.22 portal amounted to ± 9 mm in Sedrun and ± 8 mm in Biasca (see Tab. 1). This Tab. 1: The accuracy of LHN95, the comparison between LHN95, pure levelling degree of accuracy is a result of the glob- heights (LNIV) and LN02 relative to the Erstfeld portal as well as the vertical al adjustment of all measurements (po- velocities relative to the Aarburg reference point.

43 AlpTransit Gotthard

The enormous praise for the successful breakthroughs belongs without a doubt to those surveyors who persistently followed their goal under difficult and sometimes abominable conditions. Without the corresponding initial results at the portals, their efforts would have been ques- tioned. AlpTransit also posed a challenge to all those responsible for the Swiss national survey. portal Amsteg vertical shaft portal Sedrun orthom. correction orthom. [mm] correction References: Bürki B., M. Ganz, Ch. Hirt, U. Marti, A. Müller, P.V. Radogna, A. Schlatter, A. Wiget (2005): Astrogeodätische und gravimetrische Zusatz -

cut-through Sedrun cut-through north messungen für den Gotthard-Basistunnel. swisstopo-Report 05–34. Haag R., A. Ryf and R. Stengele (1996): Grund- lagennetze für extrem lange Tunnel am Beispiel des Gotthard-Basistunnels. Beiträge zum XII. Internationalen Kurs für Ingenieurvermessung,

Heigh [m o. Sea] Graz. Haag R. and R. Stengele (1999): Vermessung- stechnische Grundlagen und Herausforderun- gen beim Projekt «AlpTransit – Gotthard Ba- sistunnel». VDI Berichte 1454, VDI- Gesellschaft Bautechnik. Fig. 5: A priori orthometric corrections in the tunnel based on orthometric Gerber P. (1974): Das Durchschlagsnetz zur heights in the portals. Gotthard-Basislinie. Mitteilungen aus dem In- stitut für Geodäsie und Photogrammetrie der it was possible to determine a solid height • The influence of the alpine uplift on the EHTZ Nr. 17 frame for the AlpTransit GBT with only 30 fundamental height network is proba- Marti U. (1997): Geoid der Schweiz 1997. Geo - km of new measurements. A few addi- bly interesting but of minor significance dätisch-geophysikalische Arbeiten in der tional remarks: to the breakthrough itself. The uplift Schweiz Band 56. SGK 1997. • Basically it doesn't matter which verti- rates in project GBT are based on the Marti U. (2002): Alptransit Gotthard Basistun- cal frame is used for the construction of comparison of two observation epochs nel: Schwerefeldstudie. Technischer Bericht trans-alpine rail tunnels, as proved by (approx. 1920/1970). The much greater 01–36; Bundesamt für Landestopographie. the two projects Gotthard and subsidence in the Gotthard region (see Riesen H.-U., B. Schweizer, A. Schlatter, A. Lötschberg. However, without the Fig. 6) was detected rather accidentally Wiget (2005): Tunnelvermessung des BLS-Alp- Transit Lötschberg-Basistunnels. Geomatik knowledge and results of the more pre- by swisstopo in 1997. In retrospect, the Schweiz 11/2005. cise LHN95, the corresponding success portal areas were at risk of being influ- would not have been possible. enced by unknown factors. Schätti I. and A. Ryf (2007): AlpTransit Got- thard-Basistunnel: Grundlagenvermessung, • It is much more important to correctly • The claim today (or even 15 years ago) letzte Kontrollen vor dem ersten Durchlag. In- handle the various corrections, advan- that the elaborate and costly levelling genieurvermessung 2007, Graz. tages and disadvantages. This far measurements can be entirely replaced Schlatter A. (2007): Das neue Landeshöhen- greater challenge was mastered by both by GNSS observations is false. It is easi- netz der Schweiz. Geodätisch-geophysikalis- project surveys in an exemplary manner. ly forgotten that today's equally neces- che Arbeiten in der Schweiz Band 72. SGK • It is not always the newest measuring sary geoid models could at this time not 2007. technique that bestows us with better have been realized without the infor- Schlatter A. and U. Marti (2005): Höhentrans- results (see Riesen et al. [2005]). Often mation gained from LHN95 if one wants formation zwischen LHN95 und den Ge- even 30-year-old measurements will do to reach an agreeable precision. Thus brauchshöhen LN02. Geomatik Schweiz just fine. there is no sign of independence here. 8/2005.

44 AlpTransit Gotthard

Eisenbahn-Alpentransversen «AlpTransit». Beiträge zum XII. Internationalen Kurs für In- genieurvermessung, Graz. Signer T. (2002): Landesvermessung LV95: Übersicht und Stand des Projektes. Vermes- sung, Photogrammetrie, Kulturtechnik 1/2002. Heigh [m o. Sea]

Fig. 6: Subsidence at the Gotthard Pass due to the construction of the road Adrian Wiget tunnel [Schlatter 2007]. Dr. Urs Marti Dr. Andreas Schlatter Schlatter A. and U. Marti (2007): Aufbau der auf der Basis des Landesnivellements. Technis- Geodesy Division neuen Landesvermessung der Schweiz 'LV95'. cher Bericht 95–22, Bundesamt für Landesto- Federal Office of Topography swisstopo Teil 12: Landeshöhennetz «LHN95». swisstopo pographie. Seftigenstrasse 264 Doku Nr. 20. Schneider D., U. Marti and A. Wiget (1996): CH-3084 Wabern Schneider D. and R. Haag (1995): AlpTransit Die neue Landesvermessung der Schweiz LV95 Switzerland Gotthard Basistunnel: Höhengrundlagennetz als Grundlage für die Vermessung der neuen [email protected]

45 AlpTransit Gotthard

In this article, the main focus is on track Overview of railway construction, which is being carried out by a joint venture between Alpine Bau technology in the Gotthard GmbH and Balfour Beatty Rail GmbH. Outside the tunnel, there are some 20 km Base Tunnel of ballast track to the south, 16 km of same to the north and 27 sets of points, In October 2010, after many years of construction, all the key personnel involved in which are also part of the overall track the tunnel’s construction joined with politicians to celebrate the main Gotthard break- construction. Scheuchzer SA has almost through. Even before this milestone had been reached, the next construction phase completed the southern part of the track had been scheduled: the concrete casting of the tracks and the installation of all ad- in the Ticino region. ditional railway technology. Beginning in the summer of 2010, the installation of the Grunder Ingenieure AG, Burgdorf is entire railway infrastructure was achieved in a step-by-step fashion in the western tasked with all the necessary survey work tube of the Bodio – Faido section. During the operative test phase (scheduled for 2013) for the «Transtec Gotthard» consortium. the main aim will be to verify the reliability of the overall system and to discuss potential improvements. The installation of the track for the remaining 100 km will start in 2012 and will capitalize on all the lessons learned during the first construc- Project requirements tion phase. The logistical challenges are far greater in a tunnel of 56 km than on an open track line. There is no place to side step. Vari- ous processes that are independent of technology. To illustrate the dimensions each other must be carried out one after D. Stähli, M. Baumeler, Th. Silbermann involved in this immense project, one the other in order to maintain high pro- should take a look at the following de- ductivity and minimize potential interfer- tails. ence between these processes. The main In October 2010 a major milestone was In two separate tunnels (one northbound task is the «industrial production» of the reached at the site of the Gotthard Base and one southbound), comprising a total track. As different construction and sur- Tunnel: the main breakthrough itself. At length of 117 000 m of track and four veying processes follow each other, they the same time, in the Bodio to Faido sec- crossovers, around 119 000 m3 of con- have to be coordinated down to the finest tion – away from the focus of attention – crete will be laid and 234 000 m rail will detail. The goal is first, to ensure optimal the first few metres of concrete slab track be mounted over the next few years. In were laid. In an on-going process, the addition, the 180 cross-cuts will require track is being constructed on an industri- the installation of several hundred kilo- al scale within the tunnel itself. This is, in metres of cable and guidance systems to effect, the main task of the railway con- ensure that passenger and freight trains struction. This process demands the high- will be able to travel at different speeds est standards in terms of logistics, sur- through the tunnel. veying and building processes. In a few years’ time, more than 100 km of track Organization of railway will have been built to within millimetre accuracy in order to guarantee the safe technology contractor operation of the high-speed trains travel- The aforementioned demands require a ling through the tunnel. great deal of expert know-how. Four lead- The railway technology comprises all the ing companies with international experi- various technological units necessary to ence formed a consortium called enable trains to pass safely through the «Transtec Gotthard». This company com- base tunnel. Key here is the track and the prises Alpine Bau GmbH, Balfour Beatty overhead line. However, train control sys- Rail GmbH, Alcatel-Lucent/Thales, and tems, ventilation, lighting, signaling, se- Alpiq. The consortium is divided into a curity systems, electrical grounding, com- number of sub-working groups to deal munications and energy supply for the with the following areas: overhead line, trains and for all technical equipment al- track, cable construction, security, and Fig. 1: Training/sample track at the Bi- so form vital parts of the required railway train control technologies. asca surface installations site.

46 AlpTransit Gotthard

rough adjustment, moves the track to about ± 3 mm in position and –3 mm in elevation. This is precise enough to carry out the installation of all objects that have to be positioned relative to the track. Af- ter completing all track work and just hours before the concrete placement, a last surveying process is executed: the track is precisely adjusted to the design axis with sub-millimetre accuracy in position and elevation. On the seventh day of each 20-day working interval, the concrete placement starts. With the help of the newly designed mobile concrete factory (based on a 480 m long train) an average of 200 m of slab track is built each day. This factory carries all necessary concrete ingredients (including cement, gravel, water and addi- Fig. 2: Adjustment of the training track. tives) into the tunnel. On site, the concrete is mixed and each load is checked construction progress, and second, to The rest is being done from the Biasca in- and verified by the mobile laboratory. A provide the necessary conditions required stallation site in Ticino. Each of the six sec- special transportation system (which runs for surveying work (e.g., elimination of vi- tions is divided into working phases with on the shoulders on either side) brings the bration). a maximum length of 2,160 m. This odd concrete to the casting site. There the con- All logistical planning is dictated by the number is due to the length of the rails crete is systematically placed around and rate of track installation itself. This has being used (120 m each). A working beneath the single blocks. The casting it- therefore, the greatest influence on all phase lasts 20 days, during which the en- self lasts about 10–11 days and is followed other aspects. Prior to the track section tire superstructure is built. The next work- by the various completion works. After 20 being put down, a special vehicle lays all ing phase begins immediately after the fi- days this phase ends and the very next cables in their respective cable ducts. Then nal day of the previous one, i.e., there is day, the new phase begins. there is the laying of the tracks them- no break in the construction. The first sec- selves. After that, all work is carried out tion of the tunnel is due to be completed from track-based vehicles. This is also the in eight working intervals and, therefore, case for the surveying processes. finished by March 2011. A working phase consists of the follow- Installation process of the ing steps: At the outset, the rails for 2,160 m of track are inserted into the tunnel and slab track put onto the concrete floor. They are fixed On the installation site outside the south- with the help of spacers to ensure the cor- ern tunnel portal, a 250 m long train- rect gauge and are then welded. On the ing/sample track was built. Here all the following day, all booted single blocks of specifically constructed machinery is test- the LVT-system are laid out along the en- ed before being used in the tunnel. Sim- tire track. A specially designed wagon ulations of the interaction between sur- puts them in between the rails onto the veying and building processes are also tunnel floor. In addition, all further equip- performed at this site. ment needed to fix the track is brought The planning process sees all work in the into the tunnel. Hereafter, mounting the tunnel being divided into six sections, track begins with the help of a specially each of them between 16 and 20 km long. designed shifting system. The mounting Two-thirds of the project is being man- itself is done to within an accuracy of ± aged from the north tunnel portal at Er- 15 mm in position and –10 mm in eleva- Fig. 3: Cement train heading for the stfeld and its northern installation site. tion. An initial surveying process, called Bodio portal.

47 AlpTransit Gotthard

termines position and elevation of the track. Leica T30 Total Stations are set up as free stations by using eight surveying points and then measuring the start and end of these chords. After the laser chord is aligned, it is then pointed onto an active target board mounted on the trolley. Depending on the laser position on the active target board, the track position is calculated and the offset of the track to the design position/elevation is shown in real time by the system.

This method ensures a high relative accuracy of the constructed track and one that is far beyond the accuracy of systems without a laser chord. Experience so far has shown that the system ensures the daily performance targets in terms of quantity and quality are achieved.

Fig. 4: Track laying in the section Bodio – Faido West. Thereafter, the stakeout of all remaining railway system installations is done with Survey work sults. Permanent monitoring and report- the help of hydraulic lifts. This includes ing of all surveying steps is an integral part the overhead wire, radio cable mount- All rail technology-related surveying tasks of the applied quality management. This ings, beacons and signage for the main are listed below. includes protocols of the track position signals. This is carried out on the section After the hand-over and verification of the before and after the concrete is poured. between the portal and the furthermost project data, such as axis, cross-profiles All track adjustment processes are real- point of the laid track. This means the and surveying points, the dimensions of ized with the track measuring system track has to be used daily by the train with the completed tunnel have to be checked from Intermetric GmbH. This system is the mobile concrete factory. All stakeout and verified. Are the floor and shoulders basing on a fixed laser chord, which de- work, even if far apart, has to be coordi- built to within accepted tolerances in terms of position and elevation? This information is very important in order to ensure a smooth installation process for the track. In a further step, survey points are set out every 20 m along a shoulder. These are used as reference points for mounting the track to an accuracy of ±15 mm without the need for surveying staff on site. During this process, rail inclination is also aligned and the single blocks are mounted onto the rails with the correct distance between them. A track measurement trolley is used to Laser align the track to a very exact degree. The alignment is done in two runs. The accuracy requirements are within a tiny range base points of just a few tenths of a millimetre. There- sleepers positioned with total station fore, the most accurate devices on the track measurement trolley market are used. All process steps are op- intermetric target plate timized in terms of the law of error propagation, in order to get best possible re- Fig. 5: Functional diagram of the track measurement trolley.

48 AlpTransit Gotthard

ing and to be able to contribute our efforts towards the successful completion of this record-breaking project.

Daniel Stähli dipl. Kulturing. ETH Grunder Ingenieure AG Bernstrasse 21 CH-3400 Burgdorf [email protected]

Martin Baumeler dipl. Ing. ETH Grunder Ingenieure AG Bernstrasse 21 CH-3400 Burgdorf Fig. 6: Measurement screen of the track measurement trolley. [email protected] nated within the entire construction This initial phase of the track installation Ing Thomas Silbermann process. is a very interesting one. The first few hun- Transtec Gotthard Consortium – After completing the railway technology dred-metres inside the tunnel have been Track Construction installation, every single part is measured built but more than one hundred kilome- Alpine Bau GmbH in terms of its absolute position and the tres have yet to be completed over the Hansmatt 32 data are imported into the Swiss federal coming years. It is immensely satisfying to CH-6370 Stans railways’ infrastructure database. be part of such an interesting undertak- [email protected] Illustrations

49 AlpTransit Gotthard

of the standard deviations for the angle Measurement Uncertainty as well as the gyroscopic measurements, only random measuring errors were pre- of Gyro-measurements in the sumed. Therefore only a probability of p = 68% can be allocated to the statistical Construction Works of the values calculated by both equations. For additional probabilities of p = 95% and p Gotthard Base Tunnel = 99% the appropriate values can be taken as well from the graphs. It should be In large tunnel projects like the Gotthard Base Tunnel (GBT), with a length of 57 km, mentioned that the last case has a special additional gyroscopic measurements are very important contributions of geodetic con- relevance, because the hereby given in- trol measurements. This article once again demonstrates the unfavorable propagati- terval ± q can directly be compared with on of random and systematic errors in the unavoidably long stretches of the measu- an indicated measuring tolerance. ring configuration of tunnels. In contrast the increase in of accuracy is discussed when In summary, however, it can be read from the orientation is supported by gyro measurements. The main emphasis, however, is the two graphics that both measuring in the discussion of the influential quantities of these specific measurements and on procedures differ in the expected lateral the realistic estimation of the standard uncertainty of the orientation measurements error by a factor of approximately 20; even carried out in the GBT during the whole construction period. Furthermore, it is pro- by considering only random measuring er- ven that these measurements could not only increase accuracy and reliability but al- rors in the traverse measurements it holds so reveal by an adequate measurement layout such systematic errors as horizontal re- that the given measuring tolerance can fraction. no longer be kept, especially in longer tunnel constructions. Therefore, additional precise gyro measurements will be inevitable either to increase accuracy or for reliability aspects. Note, for different reasons it will not be feasible to independently orient every tra- For a one-sided connected, stretched traverse leg with gyro measurements. There- H. Heister, W. Liebl verse with n equal legs d and a total length fore, the question that frequently arises is L one can state the approximation for- how often and at which positions should mula for the statistical uncertainty of the gyro azimuths be measured. In principle, Today gyroscopic measurements are an lateral error as this question can be answered properly essential contribution to geodetic control only for known, practical projects. But measurements in connection with large there are theoretical considerations that , tunnel construction projects. On the one can support at least the decision for this. hand this lies with on the fact that After Halmos [1976], the optimization tachometer measurements, in particular in which is the standard deviation of a problem yields the following solution: in with regard to the unavoidably long measured angle. principle only the optimum is then achiev- stretches of the measuring configuration, The same approach can be considered for able, if the orientation measurements are produce an unfavorable propagation of a gyro traverse in which every leg is ori- symmetrically distributed over the total random and systematic errors. On the ented by a gyroscopic measurement with traverse length L. Thus, for a free traverse, other hand, the systematic measuring er- a standard deviation Sk. Now the lateral in which a number of z gyro measure- rors – mainly the horizontal refraction – error yields ments are planned, the following gener- can hardly be compensated for by modi- al rule can be applied: fied measuring arrangements. . Although much has already been report- ed in detail in the past on optimized se- tups of gyroscope measurements (Tárczy- In the following Fig. 1 the statistical lat- Hornoch, in 1935, Halmos, in 1972), eral errors - calculated by both formulae If z = 1, then only one gyro measurement some differences in error propagation of - represented a special but typical case of is intended. The location for this mea- gyro and tachometer measurements are equal side lengths of d = 250 m and dif- surement lies around ½ L that means in presented again here as an exemplifica- ferent traverse lengths L. It should be em- the middle of the traverse. For z = 2 the tion. phasized again that for the default values zones can be quoted as ¼ L and ¾ L. For

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of the measurand, because of random effects and the imperfect correction for systematic components. In the preceding explanations for the determination of the expected lateral error only random effects were considered, but this concept allows for the inclusion of systematic errors. The quantitative evaluation of the uncertainty generally comprises the determination of several components, which may be grouped into two categories:

A: Components, which are evaluated by statistical methods. B: Components, which are evaluated by other means.

The components of type A will be stated by the empirical standard deviation si and

its degree of freedom vi. The computa- tional methods like least squares, the combination of standard deviations by the law of propagation, and the consideration of correlations are well known to all Fig. 1: Statistical lateral errors in stretched traverses, without and with gyro geodesists. The uncertainty component measurements. uAi = si, based on these statistical methods, is called the standard uncertainty. z = 3 the zones finally are located at 1/6 fluence quantities, which can occur in The components of type B can be re- L, ½ L and 5/6 L, etc. tunnel surveys, to the uncertainty budget. garded as approximations of an associat-

Through only one gyro orientation of qw These can arise typically in the instrument ed standard deviation and are character- the last traverse leg, just before the head- as well in the environment of the mea- ized by uAi = si,, which is usually based on ing face in a free traverse, the value of qw surements. scientific judgment using all relevant in- can be cut in half. If additionally in the formation available. Unfortunately this middle of the traverse another orientation approach is rarely applied in geodetic is measured, then the lateral error can be The concept of metrology. The proper use of the pool of reduced again by the factor 0.5. If instead information is a skill that can be learned two symmetrically distributed gyro az- measurement uncertainty only with experience and practice. It imuths were determined, the reduction In the last decade in geodetic/surveying should be recognized that a type B eval- factor yields 1/9 [Jordan, Eggert, Kneißl, measurement techniques the concept of uation of standard uncertainty could be 1967, p.582]. This makes clear that by rel- uncertainty in measurement became as reliable as a Type A evaluation. atively few but accurate gyro measure- widely accepted. The definition and gen- The estimated standard deviation, which ments the statistical lateral error, even as- eral rules of uncertainty as a quantitative can be attributed to a measurement re- suming a probability of p = 99%, can be attribute to the final result of measure- sult, is obtained by combining all individ- minimized considerably within the given ments was developed in the 1990s and ual standard deviations, whether arising measuring tolerance. first published in the Guide to the Ex- from a Type A or Type B evaluation and is

These statements are not new, however, pression of Uncertainty in Measurement denoted uc, combined standard uncer- the conclusions are based only on the con- (GUM) as an ISO document in 1995 [BIPM, tainty. It is calculated by the law of prop- sideration of random errors and the here- 2008]. agation of uncertainty: in related experimental standard devia- The definition of the term uncertainty is, tions sw and sk. For this reason the focus that the measurement result, obtained af- of the following explanations is to addi- ter correction of all recognized systemat- tionally include the main systematic in- ic effects, is only an estimate of the value

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influence, which can affect different types of systematic errors. Some of them may be corrected, but some will still remain In a normal case, it is sufficient to report This short summary of the guidelines for and influence the measuring result. All the uncertainty u respectively uc as a pos- evaluating and expressing the measure- this has to be considered in the uncer- itive value together with the measurement uncertainty was targeting the ap- tainty budget of the measuring result – ment or measurement result. But for some plication in tunnel survey and particular- the gyro azimuth. In principle the uncer- applications, especially where higher con- ly for gyro measurements. A more exten- tainty components can be distinguished fidence intervals are required – e.g., tun- sive description for calculating standard in nelling – or where the relation to toler- uncertainties under different probability • instrument related components, ances must be specified, it is advised to and distribution requirements is given in • components due to corrections (reduc- indicate an interval as a measure of un- Heister [2005a, 2005b] and BIPM (GUM). tions), certainty. The uncertainty intended to • components caused by influence quan- meet this requirement is termed expand- Uncertainty components of tities of the measuring environment. ed uncertainty U, and is obtained by mul- It is impossible to discuss all influences in tiplication with the coverage factor k: gyro measurements detail in this contribution – for this rea- With the GYROMAT of the Westfälische son refer to Halmos [1971], Heister [1990;

U = k ·uc Berggewerkschaftskasse (WBK, today 1992], Korritke [1997], and Grillmayer DMT, Essen, Germany) at the end of the [2003]. In this contribution, only the most In general the range for k = 2 is chosen, 1970s [Eichholz, K. and Schäfler, 1978] important, prior systematic effects will be which will define a level of confidence of the first automated high precision gyro discussed. approximately 95%. To specify the inter- theodolite was presented and commer- val, the value of the expanded uncertain- cially available on the civilian market. Stability of the calibration value ty is quoted with signs ± U. This instrument can be considered as a Though the band suspended north seek- The proper and complete estimation of all reference in tunnel projects and was ing gyro theodolite is an absolute mea- influence quantities requires comprehen- therefore utilized as well by different in- suring system, the numerical relationship sive knowledge of the internal measuring stitutions in the Gotthard Base Tunnel. between gyro and theodolite readings is process of all instruments used, the con- Though this instrument has reached a provided by an instrument constant called ception of the measuring method, and fi- high level of automation and can look the calibration value E. Due to assembling nally the effects of the environment. In back to a long history of development, of the instrument, transportation and this context, all classical, statistical meth- there will still remain some quantities of shocks as well due to maintenance and ods will not provide a solution to quantify a measure of accuracy, thus approaches are demanded for realistic and representative estimations of Type B uncertainties. This also is meaningful in all cases where the redundancy of the measur- and is very poor and, therefore, its empirical standard deviation has a very large variance.

For practical calculations the GUM will provide various possibilities to allow input quantities of different distributions and probabilities: • normal distribution with a probability of 50%, 68% and 100%; • uniform distributions in an interval a – to a + ; symmetric and asymmetric with respect to the best estimate of the measurand; symmetric triangular distribution; Fig. 2: Changes of the calibration value of the GYROMAT 2000, Ser. No. 225 • etc. during use in the GBT.

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aging this value can change. Therefore it is necessary to regularly check or re-determine this important constant. An important possibility to detect changes of E lies in the design of the measuring concept. Fig. 2 demonstrates the changes in the calibration value of the GYROMAT 2000, which was used during construction works of the GBT.

Internal temperature changes of the instrument The GYROMAT is a highly complex opto- electronic but also a mechanical measuring system, in which temperature changes in different components effect measuring errors. This requires a comprehensive test Fig. 3: Changes of the measurand of the GYROMAT 2000, Ser. No. 225 as a func- program during the manufacturing tion of the internal instrument temperature. process in order to determine temperature dependent corrections. Intensive investigations have revealed [Heister, 1992, measuring setup. Hence, the following forward and reverse gyroscopic measure- Grillmayer, 2003] that nevertheless sig- advice should be considered: ments the refraction influence will be- nificant residuals – differing from instru- • sightings near the wall should be avoid- come measurable. The difference of both ment to instrument – will still remain. For ed in all cases; measurements can be explained inter alia this reason the GYROMAT of the Institute • around the center line of the tunnel a by these effects [Heister, 1992]. Therefore of Geodesy was again calibrated inde- thermally stable area exists that allows gyro measurements are suited to locate pendently for these temperature effects. almost refraction free measurements; sightings, where the influence of refrac- The results are presented in Fig. 3. • diagonal sightings are 70% less influ- tion potentially may occur. From this one can derive a calibration enced by refraction than sightings near function, which provides individual tem- the wall; Gyro measurements in the perature corrections for each measure- • for orientation transfer near the portal ment. The reference temperature is 20°C. of the tunnel, the thermally unstable GBT Fig. 2 as well demonstrates clearly, that area should be widely bridged. In the context of the unique Gotthard large temperature differences, that may To estimate possible refraction influences Base Tunnel project, the Institute of Geo- occur in wintertime between measure- d(t) the following approximation formula desy of the UniBw Munich, among other ments taken outside in the portal network can be applied: technical institutions, was assigned to and in the tunnel just behind the TBM, perform the orientation measurements cannot be neglected. for monitoring the routine tunnel survey by high precision gyro measurements with Horizontal refraction E.g., for a D = 300 m long sighting and the GYROMAT 2000. To establish the con- The deflection of the optical line of sight assuming a horizontal temperature gra- cept for these measurements, the authors by the horizontal temperature gradient dient of grd t = 0,3 °C / m the refraction benefitted from the practical experiences produces in almost all geodetic measure- angle d(t) already yields 10’’. at the Lötschberg Base Tunnel. ments an influence quantity, which caus- All this points out that, on the one hand, Control measurements for orientation es considerable systematic measuring er- the horizontal refraction will influence the took place in the five portal networks of rors. In particular in tunnel surveys these accuracy of the lateral error considerably, Erstfeld, Amsteg, Sedrun, Faido, and Bo- systematic effects must be observed very while on the other hand, the refraction dio and, of course, in the intervening tun- carefully. Practical investigations have angle d(t) is a function of parameters, nel sections. In the period between Au- proved [Heister, 1997] that measuring er- which in praxis cannot be captured ade- gust 2004 and April 2010 six field cam- rors in the horizontal angle of some 10’’ quately so that corrections of the mea- paigns took place. In this period with the are no rarity. In principle this phenome- sured angles can be determined. GYROMAT 2000, Ser. No. 225, measure- non can be minimized by an appropriate It is still worthwhile to mention that by ments were performed permanently as

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well reference measurements on the • refraction influences were recognized, azimuth calibration baseline of the Geo- and detic Laboratory of the UniBw Munich • the stability of the local reference lines and four extensive temperature calibra- could be monitored. tions in the environmental chamber. The operation chart for a measuring campaign resulting from these conditions is Concept for the gyro measurements given in Fig. 4. All measuring procedures for the transfer All gyro measurements by the GYROMAT of orientation were designed so that 2000 were controlled wirelessly by a PDA • the specified measurement uncertainty so that manual interventions at the in- of < 3,3” could be ensured, strument during the sensitive measure- • all measurements were verified inde- ment could be avoided. The automated pendently, data transfer immediately offered the • changes in the calibration value were evaluation including all corrections and

detected, reductions of the gyro bearing tK in the projection system of the Swiss legal survey: Fig. 5: Gyro measurements with GY- tK = A + E0 + DE + vT – dA + da – c + dT , ROMAT 2000, Instr. No. 225, version where Unibw (wireless controlling, data transfer and evaluation with PDA). A the raw azimuth (original gyro measurement),

E0 calibration value, determined on the This high magnitude of gyro measure- calibration baseline of the UniBw ments allows for some statistical analysis Munich, concerning accuracy and influences of the DE local correction of the calibration val- environment. First Fig. 6 represents the ue: ELOK = E0 + DE, empirical standard deviations of all single

vT temperature correction, reference measurements and means of the series of 20°C, measurements. dA correction due to the deflection of Averaging over all series of measurements the vertical, the following accuracy conclusion can be da reduction due to the height of the stated as compiled in Table 1. target point, The environment outside and inside of the c meridian convergence, tunnel can be characterized by the pre- dT reduction of the bearing into the pro- vailing temperatures. These values and jection system. the resulting corrections are listed in Table 2. Over all in this project 1383 gyro mea- The differences of forward and reverse surements were taken for the following measurements on the reference lines and reasons: on the traverse legs in the tunnel allow • 130 measurements on the calibration conclusions to be drawn concerning the baseline of the UniBw Munich, before horizontal temperature gradient and pos- and after each campaign at the GBT; sible horizontal refraction. • 555 measurements for temperature cal- The compilation in Table 3 demonstrates ibration in the environmental chamber clearly that on average – except in a few of the Geodetic Lab of the UniBw Mu- cases – there was no significant effect of nich; potential horizontal refraction. This indi- • 100 measurements on the calibration cates as well a good reconnaissance of baseline of the UniBw Munich, before the local reference lines and a good loca- and after temperature calibration; tion of the tunnel traverse. Here the Fig. 4: Operation chart for gyro mea- • 598 measurements at the GBT in 116 arrangement in the middle of the tunnel surements in the GBT. series of measurements. was preferred, where we – as already

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proved – have minimal influence of refraction. Once again this advantageous measuring set-up has been proven in the GBT project and has positively influenced the error propagation in horizontal angle measurements.

Estimation of influence quantities To come to a representative quotation of the measurement uncertainty of gyro measurements according to the GUM, it is necessary to estimate as completely as possible the uncertainty components of a Type A and Type B evaluation. In agreement with formulae given above and the systematic effects discussed in the previous paragraphs, we can assemble the following uncertainty budget: Fig. 6: Standard deviations of the single gyro measurements and the mean of the measurement series. 1. Measurements on the reference line in the portal network and determination of

the local calibration value ELOK. Standard deviation of Mean Minimum Maximum [’’] [’’] [’’] Gyro measurement (mean of forward a. reverse) (s. table 1) the raw azimuth a : sa 3.4 0.4 8.9 uȉA ref = 1.2’’ (Typ A)

the mean A : sA 1.5 0.2 4.2 v Temperature correction T (s. calibration sheet) the mean of forward a. uv = 0,7’’ (Typ A) reverse measurements ȉA : SȉA 1.1 0,1 2.9 T

Table 1: Standard deviations of raw azimuths (original gyro measurements). Correction for the deflection of the vertical dA

with sh = 0,5’’ yields approximately sh

Ȃ udA Gyro-Temperature [°C] Temperatur Corr. vT [’’] udA = 0,5’’ (Typ B) Portal network Tunnel Portal network Tunnel Locally derived bearing t Maximum 26.6 31.9 2.3 4.8 R utR =1,3’’ (Typ B) Minimum –5.5 12.7 –4.1 –0.4 Mean 10.2 25.1 –0.9 1.5 Centering error of the instrument e e = ± 0,3 mm (uniform distribution) Table 2: Gyro temperatures and corrections. u(e) = 0,58 e = 0, 17 mm (s. Heister, 2005 a,b) assuming for the distance 500 m between

Differences of gyro bearings tK Mean Minimum Maximum instrument and target point

between forward and reverse [’’] [’’] [’’] ue = 0,1’’ (Typ B)

Portal network 1.2 0.0 4.5 Horizontal refraction can be neglected, as Traverse legs in the tunnel 1.. 0.0 5.3 there was no significant detection at all GBT measurements. Table 3: Differences of gyro bearings between forward and reverse measurements.

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Following the law of uncertainty propa- Attributing a grade of confidence to the Finally it can be pointed out that the com- gation for the local calibration value ELOK gyro bearing of the tunnel traverse leg pilation of an uncertainty budget in ac- the combined standard uncertainty yields: (analog to the statistically defined confi- cordance with the Guide to the Expres- sion of Uncertainty (GUM) can offer, aside from the introduction of statistical quantities, the consideration of additional information including practical knowledge 2. Gyro measurements of the traverse legs dence interval) one can state with the cov- of specific measuring procedures [BIPM, in the tunnel (analog to 1.) erage factor k = 2 the expanded uncer- 2008]. Hence, a much more representa- tainty tive quantification of the specific measure Gyro measurement (mean of forward a. of accuracy, the uncertainty, is given. In reverse) U(tK) = k · uc(tK) = 2 · 2.8’’ particular, the statement of the expand- uȉA = 1,2’’ (Typ A) ed uncertainty, an interval similar to the Hence the expanded uncertainty of a gy- tolerance, can facilitate the interpretation v Temperature correction T ro bearing derived from the orientation of and use of the derived results for all col- (s. calibration sheet) the portal network yields for the GBT pro- leagues not so familiar with statistical es- uvT = 0,7’’ (Typ A) ject timation theories.

Correction for the deflection of the verti- U(tK) = ± 5,6’’ References: cal dA BIPM (GUM) (2008): Evaluation of measure- s s with h = 1,0’’ yields approximately h Ȃ This accuracy statement can be regarded ment data – Guide to the expression of un- udA as an interval, in which with a probabili- certainty in measurement. JCGM 100. udA = 0,5’’ (Typ B) ty of approximate 95%, the measuring BIPM (2008): Evaluation of measurement data result can be located. – Supplement 1 to the «Guide to the expres- Centering error of the instrument e sion of uncertainty in measurement» – Propa- e = ± 2,0 mm (uniform distribution) gation of the distributions using the Monte u(e) = 0,58 e = 1,2 mm (s. Heister, 2005 Final conclusion Carlo method, JCGM 101. a,b) It was demonstrated that in large tunnel Eichholz, K. und Schäfler, R. (1978): «Gyro- assuming for the distance 350 m between projects, where lengthy stretches of mea- mat», ein automatischer Vermessungskreisel hoher Genauigkeit und kurzer Messzeit. Mit- instrument and target point suring configurations cannot be avoided, teilungen aus dem Markscheidewesen, Jg. 85, u = 1.0’’ (Typ B) gyroscopic measurements are indispens- e S. 281–293. able, for accuracy augmentation as well Grillmayer, E. (2003): Untersuchungen sys- 3. Uncertainty budget for determination as for reliability. Additionally we can ob- tematischer Fehlereinflüsse bei Messungen mit of orientation of a tunnel traverse leg tain important information with regard to dem Kreisel DMT Gyromat 2000. In: Brunner, (s. previous formula for calculation of the instantaneous measuring environ- F.K, (Hrsg.): Schriftenreihe des Instituts für In- a gyro bearing) ment and the resulting systematic effects. genieurgeodäsie und Messsysteme der tech- The gyroscopic measurements, carried nischen Universität Graz, Shaker Verlag, For the combined standard uncertainty of out at the Gotthard Base Tunnel, have Aachen. the gyro bearing tK we obtain shown that the measuring concept of ori- Halmos, F. (1971): Systematic and random entation transfer has led to reliable mea- errors of direction measurements with gyro- suring results. Even over the long dura- theodolites. MOM Review, 4, S. 24–32. tion of this project, changes in the local Halmos, F. (1972): Zeitbedarfs- und Genau - Regarding the numerical values, obtained reference lines in the portal networks igkeitsuntersuchungen bei Polygonierungen under 1. and 2. could be detected. The intended objec- mit Orientierungs- und Winkelmessungen. tive to provide for the independent ori- Das Markscheidewesen in den Sozialistischen Ländern, Bd. 6, S. 5–67. entation transfer of an uncertainty of better than 3.3’’ was clearly reached. With Heister, H., Lechner, W., Schödlbauer, A. and finally this high accuracy, it could be verified sig- (1990): Zur Genauigkeit und Kalibrierwertsta- bilität automatisierter Vermessungskreisel. In nificantly that the proven measuring con- Schödlbauer, A.: Moderne Verfahren der Lan- uc(tK) = 2.8’’. figuration in the middle of the tunnel desvermessung, Schriftenreihe des Studien- (Heister, 1992, Korittke 1997) prevented gangs Vermessungswesen der Universität der largely systematic effects, e.g., horizontal Bundeswehr München, Heft 38-2, S. 501– refraction. 528.

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Heister, H. (1992): Zur Anordnung von Geoinformation und Landmanagement, nauigkeit. Mitteilungen der Berg- und Hüt- Kreiselmessungen unter besonderer Berück- 11/2005, S. 604–607. tenmännischen Abteilung, Sopron. sichtigung von systematischen Fehlerein- Heister, H. (2005b): Zur Messunsicherheit im flüssen. In: Matthias, H.J., Grün, A.: Inge- Vermessungswesen. Geomatik Schweiz, nieurvrmessung 92, Beiträge zum XI. Interna- Geoinformation und Landmanagement, tionalen Kurs für Ingenieurgeodäsie, Bd. 1, 12/2005, S. 670–673. Ferd. Dümmler’s Verlag, Bonn, S. I 7/1–7/ 14. Jordan/Eggert/Kneissl (1963): Handbuch der Heister, H. (1997): Experimentelle Unter- Vermessungskunde. Band II, Metzlersche Ver- suchungen zur Horizontalrefraktion im Tun- lagsbuchhandlung, Stuttgart, S. 572 ff. nelbau. In: IX. Internationale Geodätische Korittke, N. (1997): Zur Anwendung hoch- Woche Obergurgl 1997 – Fachvorträge, Insti- präziser Kreiselmessungen im Bergbau und Prof. Dr.-Ing habil. Hansbert Heister tut für Geodäsie, Universität Innsbruck, Insti- Tunnelbau. Geodätische Schriftenreihe der Dipl.Ing. Wolfgang Liebl tutsmitteilungen, Heft 17, S. 79–91. Technischen Universität Braunschweig, Nr. 14. Institute of Geodesy of the UniBwM Heister, H. (2005a): Zur Messunsicherheit im Tárzcy-Hornoch, A. (1935): Die durch den Ein- DE-85577 Neubiberg Vermessungswesen (I). Geomatik Schweiz, rechnungszug erzielbare Orientierungsge- [email protected]

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are performed every 5 years, and the dam Automatic Monitoring of large operators implement manual and automated monitoring. Permanently installed Dams in the Swiss Alps during devices like plummets, seepage water me- ters, and gap measuring devices check the Construction of the Gotthard dams continuously for possible changes. Level 2 is comprised of special distance Base Tunnel (57 km) and angle measurements, which in some cases are performed several times per A variety of automated geodetic measuring systems have been installed at the three year. This paper elaborates only the con- dams, Curnera, Nalps and Sta. Maria, in the Swiss Vorderrhein valley to monitor pos- cept and implementation of the level 3 sible terrain deformations caused by the construction of the Gotthard Base Tunnel. monitoring system and the experience af- After several years of experience it can be said that the systems serve the intended ter 10 years of operation. The third level purpose, that valley sides – contrary to expectations – experience natural cyclic mo- is comprised of monitoring measure- vements, and that the impact of the tunnel construction can be significantly measu- ments on behalf of AlpTransit Gotthard red at the earth’s surface. AG, the builder of the Gotthard Base Tun- nel, for the control of project risks when passing underneath the dams.

1.2 Assignment of the 57 km Gotthard Base Tunnel pass- The broad scope of level 3 includes the D. Salvini, M. Studer es underneath the dams’ area of influ- wide area monitoring of the terrain in the ence. Risk analyses have been conducted vicinity of the three dams in the Alps (ap- 1. Introduction that assessed the probability of the oc- prox. 2000 m asl). More specifically, it in- currence of a damaging event as very volves the mapping of the natural state 1.1 Initial situation small, but the resulting damage as very of the terrain at geologically representa- In spite of the depth of rock of up to 2500 large. Therefore, a variety of risk reduc- tive locations before any possible impact m, tunnelling of the 57 km Gotthard Base tion measures have been imposed. by the tunnel construction. Furthermore, Tunnel through the Swiss Alps is notice- Among other things, it was decided to in- the natural behavior of the terrain is to be able at the earth’s surface. Mountain wa- tensify the monitoring of the terrain sur- understood and the surveying systems are ter emerging from the subsurface and face in the vicinity of the three dams with to be calibrated accordingly. The third and running off through the tunnel results in regard to the specific requirements of tun- probably most important task is the im- drainage of the rock. This leads to subsi- nel construction. A three-level concept mediate and reliable detection of unusu- dence at the earth’s surface. Based on the- was proposed for this purpose. At level 1, al surface movements during tunnel con- oretical analysis, these subsurface dy- comprehensive geodetic measurements struction that compromise the safety of namics were already understood during the planning phase. It was shown that surface subsidence of several centimetres could occur near the dams if appropriate measures, such as systematic and rapid sealing, are not taken during the tunnel drive. Such ample subsidence cavities can reach an expanse of several kilometres and may cause closures, openings and shear movements of opposite valley sides (Fig. 1). On the basis of the predicted surface deformations, the impacts on the three dams – Curnera (height 153 m, crest length 350 m), Nalps (height 127 m, crest length 480 m) and Sta. Maria (height 117 m, crest length 560 m) – in the Swiss Alps have been studied more closely. The line Fig. 1: Schematic representation of mountain drainage.

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the dams and require an immediate stop 2.2 Construction and Sensors of the tunnel drive. Off-the-shelf equipment was used for the During the implementation of such a geodetic sensors and the accessories of monitoring system, the requirements of the automated measuring systems. Even the client regarding accuracy (valley side for most of the electric and electronic de- movement ±4 mm, height changes mea- vices, standard components could be sured by levelling 2.5 mm/km) and reli- used. The big challenge during the in- able accessibility of results had to be tak- stallation of the measuring system was en into account. Also, the challenges of the choice of the right materials, mount- the installation and year-round operation ings, and data communication solutions. of surveying systems in alpine surround- They had to be optimized for each loca- ings during at least 12 years under the tion in order to implement a system that most adverse climatic conditions and fac- could properly function year-round under ing natural hazards (avalanches, light- the local conditions. The harsh mountain ning) were not to be underestimated. climate presents tough challenges for all installations: neither low temperatures or strong winds, nor large amounts of snow or electrostatic discharges of thunder- 2. Implementation storms must interrupt the availability of 2.1 Concept the measuring system longer than one The concept offered by the contractor, a day (Fig. 3). consortium of three surveying companies Monitoring the cross sections was imple- under the leadership of BSF Swissphoto mented by putting two total stations on AG, suggested a multi-level monitoring each of the three dam crests, and by in- system that makes use of individual stalling one total station either on the bot- Fig. 2: Monitoring perimeter and mea- strengths and advantages of different ge- tom or on a side of the valley in each of surement methods. odetic measuring technologies. The dams the three fore field cross sections (see Fig. and their immediate surroundings are 2). Including an additional tachymeter in- ceivers. When choosing the GPS sites, nat- monitored by automated total station sys- stalled as a connection between one dam ural hazards (e.g., avalanches) had to be tems. Each monitoring object is equipped and fore field cross section; ten total sta- taken into account in addition to the ge- with one or two precision total stations, tions have been in operation since 2000. ological situation. The individual GPS which execute measurements of angles Monitoring of single height benchmarks measuring stations are equipped with an and distances at prisms. The prisms are ei- is achieved by ten dual frequency GPS re- independent power supply (solar) and da- ther directly attached to the rock or placed on surveying pillars several metres high surveying pillars due to the depth of snow expected in winter. Coordinates of each prism are derived daily from these measuring elements. Based on a comparison of the spatial position of two points, transverse and longitudinal movements relative to the valley and movements in height can be determined directly (Fig. 2). Autonomous GPS measuring stations, also year-round record selective information on possible terrain movement. Preci- sion levelling along roads or through pressure tunnels is used to determine with high accuracy the spatial extent and the depth of wide-area subsidence with high accuracy. If levelling continues far enough beyond the subsidence cavity, absolute height movements can be derived. Fig. 3: Impressions of installation works.

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Fig. 4: Panoramic view of total station network in Nalps. Fig. 6: GPS station above Nalps dam. ta communication (GSM network). Fur- are present in the submission data. De- 2.4 Processing of measurements thermore, six multiple extensometers spite mature processing algorithms and Usually, deformation measurements rely have been installed and integrated into filter methods, one cannot rule out the on points that are assumed to be fixed the automated measuring process on the possibility that isolated errors may gross- and not subject to movement. In the pre- fore fields of the Nalps and Sta. Maria ly distort the results. sent case, however, terrain movements dams. These extensometers are expected The GPS measuring stations are controlled must be expected in wide areas, thus the to register possible rock movements in the directly from the computing center. They evaluation concept must be adapted, i.e., immediate vicinity of the dams. record the satellite signals weekly during the tie points are considered observation From organization of processes and un- the nights from Friday to Monday. The points at the same time. For this purpose, interrupted data flow via the program- transmission of data to the computing geodetic statistics provide the adjustment ming and automation of data processing center is also done automatically, but the method of so-called stochastic network through to submission of results, a high data processing and analysis is done man- fixation positioning. level of technical and professional know- ually. Based on the spatial distribution of the how is required. After some construc- Levelling is limited to the snow-free sea- points in the monitoring area, point pairs tional improvements based on the expe- son (usually May to October). In August can be established that describe the trans- riences of the first winter experiences the and September, two teams of three sur- verse and longitudinal movements rela- measuring systems achieve an availability veyors measure a levelling network of tive to the valley and also movements in of nearly 100% all year round. nearly 100 km in length along roads, trails height within a certain period of time. The and pressure tunnels, according to the information is summarized numerically in 2.3 Operation of measuring systems quality standards of the Swiss federal lev- the form of a half-full matrix and provid- The automatically operated tachymeter elling network (Fig. 4). ed to the client. The results are also plot- systems measure the surrounding moni- ted graphically as time/path diagrams for toring points at hourly intervals at night. easier legibility and interpretation (Fig. 5). Meteorological data required for the com- GPS measurements are processed with putation of the exact three-dimensional coordinates of the points are recorded concurrently with the geodic measurements. The data measured nightly are pre- processed the following morning by the control computers on site and transferred via email to the computing center in Re- gensdorf where they are processed automatically. Before the submission of results, an engineer checks the most recent graphs to ensure that no obvious errors Fig. 5: Graphic representation of valley closure near Nalps dam.

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the standard GPS manufacturer’s pro- paratively small amount and uniformity of • The combination of manual and auto- cessing software and subsequently im- the movements in the vicinity of the dams, mated measuring systems has proved proved using an expanded meteorologi- neither theoretical hazards nor damages ideal in various ways between the con- cal correction model. This is necessary in of the dams to any kind have been no- flicting priorities of maximized safety order to reach the highest accuracies with ticed. and an economical use of financial re- meteorologically affected GPS measure- Even the behavior of the GPS points is sources. ments. The annual levelling is processed clearly affected by the tunnel drive. The • In order to eliminate or minimize errors after completion of the measuring cam- positions of all measurement stations that cannot be compensated for (e.g., paign by means of an overall adjustment. move in the direction of the tunnel axis, induced by temperature), special ac- The results are also edited in numerical and subsidences in the range of centime- tions must be taken (e.g., limitation to and graphical form (Fig. 6). tres have been detected. night measurements, periodic calibration of total stations by the manufacturer, and so forth). 3. Results • The combination of manual and auto- The first years of operation surveyed the 4. Findings and conclusions mated data flow and analysis process- state of the terrain surface when the con- The entire measuring system has now es has two advantages: automated struction of the Gotthard Base Tunnel was been in operation for 10 years and is de- processes are time efficient and avoid still several kilometres away from the livering reliable and accurate results on a human errors, while the surveying spe- monitoring area. During this time, the daily basis. During this time, valuable find- cialists, using their know-how, check normal behavior of the terrain was es- ings have been collected that have also the plausibility of results before they are tablished, and the instruments and pro- attracted interest outside the geodetic submitted to the client. cessing methods were calibrated. Unex- world: • Wide areas of interest must be moni- pected valley openings between the be- • Due to changing ground and mountain tored with sufficient lead-time in order ginning of summer and the end of winter water levels, seasonally recurring valley to establish the situation unaffected by and rapid valley closures in early summer openings and closings in the range of construction activities and to properly were observed. These movements show centimetres occur in mountain valleys. calibrate the measurement systems. a cyclic correlation with the seasons and Up to now, this phenomenon was un- • Regular reporting to and exchange with thus with the level of mountain water. known even to geologists. the client ensure an equal understand- These seasonal, reversible movements • By levelling, a subsidence cavity can be ing of the measuring systems and their were detected in all valley cross-sections, monitored in «absolute» terms. How- limitations (e.g., as a result of short-term however, to varying degrees. The maxi- ever, the network must be designed adverse weather conditions). This is mum cyclic movements amount to up to large enough so that tie points are po- equally valid for the interpretation of the 16 mm between points on opposite val- sitioned outside the subsidence area. resulting tables and graphs. ley sides. Similar seasonal variations were Furthermore, using the same levelling observed at the GPS measuring stations. paths for several years has proven very With the approach of construction from successful. In doing so, long term move- north and south, irreversible movements ments can be interpreted much more on the terrain surface were detected, reliably and usually far below the sig- which undoubtedly had a causal rela- nificance threshold according to the tionship with the construction of the Got- theoretical measurement accuracy. Dante Salvini thard Base Tunnel. They came in the form • Autonomous GPS measuring stations Mario Studer of subsidences and concurrent valley clo- can be operated reliably even in an BSF Swissphoto AG sures (see Fig. 5). Movements ranged from alpine environment. Provided careful Dorfstrasse 53 millimetres to centimetres depending on processing and trend analysis are per- CH-8105 Regensdorf-Watt location with a maximum subsidence of formed, they meet the highest accura- [email protected] 6 cm at the moment. Due to the com- cy requirements in the millimetre range. [email protected]

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are also included in the determination of Versatile surveying outside the building site’s basic control network. It thereby becomes possible to assure that the tunnel at Altdorf–Erstfeld, the construction work, while taking into account the required accuracy of the ge- Amsteg and Faido odetic points, can be adapted in an ideal way to existing infrastructures. Since 1995, IG GEOSWISS has carried out the constructor’s surveying assignments on Today, the building site control network behalf of AlpTransit Gotthard AG (ATG). The work covers a wide spectrum of en- in the Altdorf/Erstfeld sector contains gineering surveying tasks: maintenance of the control network, pictures for project about 120 points. planning and documenting the implemented buildings, analysis of buildings, staking out of the principal axes, and monitoring various objects in order to detect deforma- Required accuracy and determination tions. All those tasks are challenging for the surveying specialists who sometimes must methods operate in very confined spaces and sometimes on vast building sites. Depending on The accuracy requirements for the con- the assignment, the surveyors have to fulfill different requirements in terms of preci- struction work are stringent. Therefore, sion. The work has to be completed according to schedule in order not to jeopardize the control network used has to satisfy the functioning of the huge NEAT building site. And sometimes a strong foehn or hea- certain minimum requirements with re- vy rains require even more efforts from the surveying teams. spect to accuracy. Basically, the accuracy between neighboring points may not exceed 15 mm in position and height. The determination of the position of the geodetic points is done terrestrially with the help of total stations: the determina- the exter-nal construction sites (outsta- tion of height through levelling. Due to U. Bättig, S. Bühler, D. Eberhart, tions) of Altdorf/Erstfeld, Amsteg, and Fai- this choice of method, the required ac- R. Bänziger do (see pictures 1, 2, and 3). Work in- curacy can be achieved. The obtained ac- cluded densification and maintenance of curacies in all areas lie within the sub- IG GEOSWISS the basic control network at the con- centimetre range. struction sites, layout work, control and In 1995, the engineering association IG monitoring, as well as different mostly Maintenance GEOSWISS was assigned the survey work smaller surveying tasks on behalf of the As a result of intensive construction ac- for the construction sites outside the Got- construction management and the local tivity at the different sections, the main- thard Base Tunnel at the Altdorf/Erstfeld, site management. tenance of the control network is of up- Amsteg, and Faido sections. The IG most importance. Damaged geodetic GEOSWISS is composed of four engi- Control network Altdorf to points and «broken» sight lines are daily neering firms. These are: occurrences. In order to ensure accuracy Erstfeld over the long term, new points are se- • Gruner AG, Basel (BS) One of the main tasks aside from the sur- cured as often as possible with SBB-bolts • Kost + Partner AG, Sursee (LU) veillance and control work lies in the den- on or at the buildings. • Markwalder & Partner AG, Burgdorf (BE) sification and maintenance of the geo- Due to the speedy construction progress • Ingenieurbüro Robert Bänziger, Nieder- detic base network (NetzGBT) at the con- and the newly erected buildings or exca- hasli (ZH) struction site. This serves the companies vated material storage, the visibility be- as a basis for their surveying work and for tween control points can rapidly change. The management lies with Gruner AG. To- specific building layout work, control, and For this reason, the site control network gether and on behalf of ATG, we carried monitoring. constantly alters and has to be regularly out the surveying tasks at the outstations completed with new points. of VI Nord (surveyor Nord), VI-A (survey- Building site control network or Amsteg) and VI-F (surveyor Faido). The building site control network is main- Control points for precision monitoring ly based on the governing base system For the millimetre-precise monitoring of NetzGBT of ATG and constitutes a densi- objects, as for instance the SBB main line, Task fication of that system. Aside from the so- local networks are used on the building On behalf of ATG, IG GEOSWISS carried called NetzGBT, the geodetic points of the site control network. With these local net- out the builder’s surveying assignments at Swiss Federal Railway (SBB) rail network works, which are exclusively used for

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tracks are monitored over a distance of approximately 3.6 km. This monitoring can be considered as the centerpiece of all monitoring. Thus at the center is the security and the guarantee of free north- south circulation: the rail traffic may not be restricted by the construction work, which takes place very close to the existing SBB tracks. The whole monitoring perimeter is divided into 7 sections, whose monitoring intervals vary according to construction activity. In the sectors with high building activity the controls take place every week, and in the sectors with low building activity only twice a month. The monitoring accuracies in position and in height lie in the range of 1 σ = ± 2 mm. To achieve such accuracies, an individual Fig. 1: Overview of the construction site of Altdorf/Rynächt up to the section control network has been created. In this of Erstfeld. network, the «free station method» is used. The SBB catenary support poles are these special monitoring tasks, accuracies do, a great number of monitoring tasks monitored. They were equipped with rein the range of 1 σ = ± 1 mm can be are necessary. The objects to be moni- flecting foil and can thus be measured achieved. For the settlement measure- tored have been included by ATG in a without stepping on the railway tracks. ments performed by levelling, the at- global monitoring concept. In the follow- The results are used by ATG management tained accuracies lie within the sub-mil- ing, typical examples of objects to be as well as by SBB experts as a basis for limetre range. monitored are described in more detail. possible interventions.

Altdorf/Erstfeld SBB main line – Railway bridge Altdorf/Erstfeld, track Monitoring the centerpiece and sheet pile wall Stille Reuss The task of VI (surveyor) is to monitor de- The longest and certainly most important Next to the existing railway bridge over formations of various objects, namely nat- object to be monitored is the SBB main the Stille Reuss another railway bridge ural objects, existing structures, and new line between Altdorf and Erstfeld. The SBB was built, on which the approach tracks ATG buildings. According to the object, different accuracies and monitoring intervals are required. There are two main reasons for such monitoring: on the one hand, the safety of the ATG building sites, and on the other hand, the security and unlimited functionality of the existing infrastructures have to be guaranteed. Most monitoring tasks are performed to guarantee the safety of the existing infrastructures and for the early detection of deformations in order to take appropriate measures. Some objects are also monitored, for evidence-protection, to document structural damage caused by deformations. As there are a great number of infrastructures in a confined zone, which often lie inside the construction perimeter at the ATG building areas from Rynächt to Altdorf, in Amsteg, and in Fai- Fig. 2: Overview of external structures and Amsteg section access tunnel.

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of the Gotthard Base Tunnel will lie in the within half an hour in order to allow for rized in tables and continuously discussed future. As the building works were ap- the possible use of the tamping and with the SBB experts. proaching the existing tracks up to about straightening machine between 5.00 and In the second phase, during the con- 1 m and were also touching the existing 6.00 o’clock, because at 6.00 o’clock the struction work of the bridge, a weekly railway bridge structure, additional local main line had to be open for the rail traf- monitoring was required. The monitoring monitoring had to be set up. The moni- fic on both tracks. The required accura- concept was maintained, as it was equal- toring of the SBB main line could not suf- cies for height and position were in the ly useful for the weekly monitoring under ficiently cover the local needs with the range of 1 σ = ± 1 mm. An intervention traffic. Also during this second phase, the catenary masts. A special monitor-ing of the tamping and straightening ma- sheet pile wall monitoring was initiated. concept was required. The existing SBB chine became necessary at a position shift tracks, the bridge superstructure as well of > 4 mm, subsidence of > 20 mm, or as the bridge foundations were moni- distortion of > 2‰. At the bridge, differ- Altdorf/Erstfeld RUAG Reusshalle tored. In a later phase, the sheet pile walls ent values applied for subsidence: alarm The RUAG Reusshalle in Altdorf is an ex- for the excavation safety of the new rail- value = 50 mm and intervention value = ample of an object to be monitored that way bridge were also monitored. 100 mm. is situated outside the construction During the first phase, when the sheet pile For monitoring, the method of «free sta- perimeter. The high precision machines, walls were driven in overnight at a dis- tion» again was used. The tracks were installed in the hall, are very sensitive to tance of one metre beside the tracks, the controlled with a track gauge and the tilting and shock. For this reason, the hall tracks had to be measured in lengths and bridge with permanently mounted SBB was monitored using two different meth- height and the super elevation/distortion track displacement measurement sys- ods. On the one hand, a precision level- on both tracks had to be controlled over tems. This made it possible to very rapid- ling was done for the evidence-protection a distance of approx. 50 m every morn- ly control the position and level of the inside the hall to observe the settlement ing between 4.30 and 5.00 o’clock. The track centerline as well as the super ele- behavior due to the adjacent building ac- evaluation had to be done reliably on site vation. The control-values were summa- tivities; on the other hand, vibration mea-

Fig. 3: Overview of landfill site Chiggiogna/Cavienca, south of the Faido access tunnel.

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surement devices were installed next to the railway line, and terrain points (Gole- Important differences in subsidence and the shocksensitive machines and a limit na-points). All the points requiring mon- position shifts have been noted spatially. value for vibrations was fixed. The vibra- itoring are situated in a very confined area. But the settlements and position shifts of tion measurement instruments recorded Similar to the Altdorf/Erstfeld SBB main- the individual objects correlate spatially. the vibrations at given sampling intervals. line, the security and the unobstructed Since the ground survey in 2000, signifi- The results could be viewed online by the north-south circulation are priori-ties. cant shifts in height and position of up to management. The responsible project engineer initially 0.30 cm were measured at individual ob- As vibration measurement devices se- defined the measuring intervals of the jects (especially at the mast foundations cured the permanent monitoring, only a subsequent surveys of the different ob- of the Gotthard main line, which lies on reference survey and a final survey were jects. Today they range from biannual sur- a dam). done with the levelling. The accuracy of veys, to quarterly surveys, to monthly sur- The various and interesting surveying the levelling was 1 σ = ± 0.3 mm. veys during critical phases. Position is tasks for this project of the century rep- measured tachymetrically with free sta- resented a technical, logistical and per- tions and the height with precision level- sonal challenge for the surveyors of the Faido landfill site Chiggiogna/Cavienca ling. The accuracy for the monitoring of engineering association. We can proudly and Polmengo position is 1σ = ± 2 mm and for height affirm that we have mastered this chal- In Chiggiogna/Cavienca and Polmengo 1σ = ± 0.5 mm. It was particularly challenge successfully. Our engineering asso- landfill sites were implemented between lenging to place the control points on safe ciation IG GEOSWISS has grown togeth- 2000 and 2002 near the main road and terrain. For the position, three control er to form a united whole. the railway line. In Polmengo, it is a tem- points were mounted on consoles on the porary deposit that will be completed. In opposite rock. The rock had to be chosen Chiggiogna/Cavienca (see picture 3), a as a solution because the entire valley permanent landfill is being created. For basin is situated in the monitoring perime- this reason, the existing infrastructures, ter and is subjected to movements. At the particularly the existing Gotthard railway beginning, the height control points were line, needed to be monitored. As a result situated on the railway track outside the Urs Bättig (Gruner AG, Basel) of detected movements during the monitoring perimeter. During the basic Samuel Bühler (Kost + Partner AG, Sursee) ground survey, the measurement range measurements, however, it was discov- Daniel Eberhart (Markwalder & Partner was continuously extended concerning ered that the height control points were AG, Burgdorf) the number of objects to be monitored also subjected to movements. For this rea- Robert Bänziger (Ingenieurbüro Robert and the expansion of the zone. Today, the son, the monitoring perimeter had to be Bänziger, Niederhasli) following infrastructures are monitored in extended gradually, and the geodetic position and height over a distance of points were fixed in the network of cadas- IG GEOSWISS nearly 2 km: the foundations of the cate- tral surveys at the rock faces and in the c/o Gruner AG nary support poles, the protective wall villages, far outside the monitoring Gellertstrasse 55 along the railway line, the main road near perimeter. CH-4020 Basel

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mately 40 points fixed in location and Monitoring Measurements height distributed around the portal area. Of these there are 10 points on top of or at Portal Erstfeld on the side of buildings in the valley within distances of up to 600 m from the por- The first 600 m of the Gotthard base tunnel in the Canton of Uri was not created by tal. With the help of a local helicopter mining, but as a surface tunnel. Up to 30 m deep, the surface tunnel cuts into the company, the prefabricated measuring ground at the foot of the mountainside in Erstfeld. Slope protection, fill and the sur- pillars were transported onto the flat roofs face tunnel are to be monitored by surveying during the entire building phase. This of chosen buildings. The points in the rock requires the highest standards of accuracy, reliability and flexibility of the measure- above the portal operations had to be in- ment technique. stalled with climbing equipment. (Fig.3). The benchmark network is seamlessly incorporated in the superior GBT network.

Surface Tunnel in Loose Construction of the Monitoring the Fill Rock Benchmark Network To monitor the eventual settlement, The actual north portal of the Gotthard As the basis for all geodetic monitoring which was provoked by the compaction, base tunnel is located where the align- tasks, a benchmark network was estab- steel rods were anchored into the ground ment meets compact rock and where min- lished, so that the stability and accuracy in various places. The rods were brought ing can excavate the tunnel. Leading up requirements could be met. In addition, it to the surface in manholes and depend- to this point, there is a 600 m-long sur- must always be available for use and re- ing on the settling behavior, could be ex- face tunnel, which is embedded into the main in place even if the construction site tended or shortened at will. The heights mountainside of loose rock (Fig. 1). In or- installations are constantly changing. The of the 21 levels were determined by us- der to keep the settlement caused by the benchmark network consists of approxi- ing precision levelling. extra impact from the surface tunnel to a minimum, the whole area is compacted with fill several metres high. Directly in front of the underground tunnel portal, the cut into the mountain has been reinforced over a length of about 200 m for the construction of the surface tunnel by using drilled piles of up to 30 m in height, which are anchored into the rock through concrete beams at various levels.

Monitoring Tasks Surveying must monitor and following objects for safety reasons:

• Pre-fill • Drilled pile retaining wall • Surface tunnel

Especially with the slope stabilization and the building work, any changes must be Fig. 1: The portal area in Erstfeld: The drilled pile retaining wall on the right known early and then compared with the secures the mining slope area immediately in front of the tunnel entrance. To predicted values. the left of it, the surface tunnel has already been created. Conveyor belts and For this purpose, both geodetic and ge- the installation area surround the construction site (Photo: AlpTransit Gotthard otechnical instruments are used. AG, Adrian Wildbolz).

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The inclinometer-pipes embedded in the piles are also measured in three-month cycles. Here, a probe is introduced into the pipe, which measures the deviation from the axis of the borehole at intervals of 60 cm. This way a statement can be made about the deformation behavior of the piles and the stability of the slope.

The Surface Tunnel The surface tunnel consists of two parallel tubes. The surface tunnel is created starting from the north since the area directly in front of the mining tunnel portal must be kept free to assemble and disas- semble the tunnel-boring machine. Inside the tunnel, approximately 30 cross-sections are monitored each with seven points. Here, a measure of tolerance of 4 Fig. 2: The approximately 30-m-high drilled pile retaining wall (Photo: Basler mm has to be maintained for the spatial & Hofmann). shift between two epochs. The monitoring points at the top of the tunnel profile In addition, two exploratory boreholes Drilled Pile Retaining Wall are equipped with mini prisms; those at were monitored with an SE probe. Safety the bottom with wall bolts and M8 adap- With the SE probes, compressions under- tor bolts. At the same time, at approxi- ground can be determined. The eventual To ensure that work can be done safety mately 35 cross-sections, settlement mea- measured settlement of up to 35 cm met in front of the tunnel portal, the two side- surements are monitored on the bottom the predictions. walls must be monitored for deformations plates of the tubes. In summer 2009, the during the entire construction period. first profiles were installed in the surface The forces on at least five percent of the tunnel. Since then ongoing follow-up rock anchors are automatically moni- measurements have been performed. tored. When exceeding the limit of tolerance, an automatic alarm is triggered, and the local construction site management is directly informed. Shifts to the South Additionally, in a three-month cycle, 60 The results of the first follow-up mea- points on the side of the drilled pile re- surements show displacements of up to taining walls are geodetically monitored. 15 mm in the tunnel’s longitudinal direc- The monitoring points are made up of per- tion. They decrease in a southern direc- manently attached mini prisms and are tion. Displacements in the tunnel’s longi- each defined by the benchmark network. tudinal direction are unusual, as one One measurement cycle consists of 10 to would expect a deformation of the pro- 15 occupied stations on the drilled pile file to occur. The reason for the displace- wall edge so that each point can be mea- ments lies in the construction of the tun- sured from at least two occupied stations. nel: The individual sections were created As the situation constantly changes with in a monolithic block with continuous re- the building progress, the occupied mea- inforcement. The temperature-induced suring positions must remain flexible to expansion of the concrete body, there- Fig. 3: Attaching the measuring points allow adjustment. Geodetic measure- fore, is not absorbed as usual by the ex- above the mining tunnel portal (Pho- ment enables the significant determina- pansion joints, but instead accumulates. to: Basler & Hofmann). tion of position shifts greater than 5 mm. Depending on the temperature, the tun-

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the view of the fixed points. In order to maintain the geodetic monitoring measurements, new occupied stations must be sought (Fig. 4). The mini prisms on the drilled pile retaining wall were often so badly polluted by the underlying conveyor belts, which re- moves the excavated material from the tunnel, that they had to be cleaned using abseiling. On the other hand, the results can be considered positive for the civil engineers: At no time did the monitored objects pose any danger to the construction site. All deformations stayed within the calculated tolerances. The measurements of the drilled pile retaining wall and the surface tunnel are to be continued until the completion of the back-fill. Fig. 4: Geodetic surveying on the drilled pile retaining wall (Photo: Basler & Hof mann). nel contracts to or expands from the Flexible Monitoring Jörg Gämperle, Michael Furrer current focal points. Since the focal point Basler & Hofmann of the tunnel shifts to the south 10 m a The construction environment demands Fachbereich GIS und Geomatik week with the advancing construction, from the surveyors a high degree of flex- Forchstrasse 395, Postfach the displacements move in this direction ibility: conveyor belts, ventilation units, air CH-8032 Zürich as well. tubes and portal cranes frequently block [email protected]

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was initiated at the Sigirino exploratory The role of surveying in the tunnel (2.7 km in length), which was necessary for the preliminary geological and construction of the Ceneri Base geotechnical analyses. In connection with this construction work the surveyors of Tunnel COGESUD were given the task to carry out the indispensable underground mea- The role of surveying in construction projects is often neglected. For the implemen- surements in order to direct the tunnelling tation of challenging structures such as the Ceneri railway base tunnel, however, it is precisely to the location of the future Op- a basic element. In the preparatory phases the surveying specialists collect and pro- erations Control Centre, CAOP. Since vide the basic geodata for the project planning. After that, they define the control then, the consortium COGESUD has ful- network outside the tunnel and determine the main points inside the tunnel to guar- filled the contractual obligations it has antee the correct orientation of the tunnelling work. Moreover, as work progresses, been entrusted with to support the con- the tunnel profiles and the external constructions (existing as well as under construc- tractor (thereinafter AlpTransit Gotthard tion) have to be controlled in order to detect possible deformations at an early stage. AG) and has concentrated on issues re- Finally, the reference points for the laying of rails and for all technical installations of lated to the surveying, specifically the con- the high-speed rail have to be moved and defined with high accuracy (under one mil- ceptual, organizational and surveying as- limetre). pects. COGESUD‘s direct partner is the geomatic section of the contractor (ATG ternal expert. He accordingly bears the re- Geomatik). With the beginning of the C. Bernasconi sponsibility for the surveying work linked main tunnelling at the Ceneri Base Tun- to the correct realization of the whole nel during 2010, the work has now en- The construction of the Ceneri Base Tun- Ceneri Base Tunnel. The tender was won tered the most complex and fascinating nel extends over a length of 15.4 km and by COGESUD, a consortium consisting of phase of the project. has a total length of ca. 40 km of tunnel five surveying companies from Ticino (see and galleries (Fig. 1). The north portal is box). in the Magadino plain on the grounds of The first work phase for COGESUD was Control networks the Camorino municipality at a height of the elaboration of the base network: a re- ReteSUD (South network) approx. 220 m above sea level, whereas liable primary network on which all future The basic positioning network for the re- the south portal is located in Vezia at a surveying work would be based. Shortly alization of the Ceneri Base Tunnel con- height of 300 m above sea level. For tech- after its completion the first tunnelling sists of the ReteSUD (South network), nical and logistic reasons big parts of the tunneling work were done from the Si- girino access tunnel. From Sigirino, the Operations Control Centre, or «Caverna operativa centrale» CAOP, can be reached through a tunnel of 2.3 km (the so-called «access window Sigirino»). The surveying experts have been involved in the project since the 1990s. They produced the cartographical base data for the tunnel and the access route project planning. The best-suited means for the data collection was the aerial photogrammetry, which resulted in precise topographic models of the extensive perimeter as well as hundreds of profiles and terrain cross-sections available to the project planning engineers in a relatively short time. In 1995, the SBB launched a public call for tender in order to transfer the role of the client’s surveying engineer to an ex- Fig. 1: Diagram of the Ceneri Base Tunnel.

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ing the LN02 height reference framework SIGIRINO CAOP-W Controllo Profili COGESUD Data Asse 25.03.09 Direzione di vista = avanzamento del CAOP-W 14 (official heights) allows for the attainment Graphik des Messprofils Massstab 1:75 Stationierung : 282.568 m Profil ID : TM282.5 DBNr. : 6 STNr. : 1282 of the requested final accuracy. In July 12 Vermesser : Cattaneo Messdatum : 10.5.2009 11:57 Instrument : TCRP1201 (SN: 213609)

. 0 7

5 0 2 . 59

5 Koordinaten der Achse . 5

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. 0 0 6 Ost : 717'495.452 m 0 2 8 . 5 4 5 . Nord : 104'510.849 m 0 6 0 0 . 9 . 6 Höhe : 274.692 m 4 0 . 7 0 4 0 10 . 6 2004, levellings were carried out at the 3 . 0 8 Auswertung 0 6 6 . . 2 0 7 9 0 .6 Referenzprofil A : CAOP-W.3 35cm (No. 2) . 2 0 8 0 3 6 Querneigung : 0.000 % . . 2 0 7 Referenzprofil B : CAOP-W.3 (No. 1) 0 4 6 .2 0. 8 0 5 6 .2 0. 7 three portals in order to exclude local sub- 0 64 .2 0. 8 5 0 8 . 5 28 0. 0. 0 32 .5 0 0 .4 7 6 .3 0. 0 57 sidence between the control point groups 21 0.6 0. 6 3 0 .15 .62 0 0 0 0.2 .59 26 0 0. .58 in LN02. The control results showed only 6 0.2 0.58 4 0.26 0.59 0.28 0.57 0.27 minimal movements. 0.51 0.22 0.40 2 0.20 0.34 0.18 0.28 0.1 0.16 8

0 0.07 . 0.14 0 0 -

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1 1 1 1 . 1 2

2 1 1

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0 0 0 0 0 0 0

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. Portal and construction control 0

-2 Misurazione parete grezza Referenzprofil A: CAOP-W.3 35cm NB: Dati del progetto asse 04.06.2009 10:16 network "piano ITC.PES.851.0301B" TMS OFFICE COGESUD c/o Gisi e Bernasconi SA Via Lugano 2A 6924 Sorengo Tel +41 91 960 17 50 Fax +41 91 960 17 55 In order to obtain a perfect stakeout of -8 -6 -4 -2 0 2 4 6 8 10 Fig. 2: Staking out in the tunnel. the main points in the tunnel and to connect all construction sites with sufficient Fig 4: Monitoring of the excavation which is composed of 24 geodetic points. accuracy to each other, a densified con- profiles. Those points are situated between Biasca trol network is needed. Therefore, the and Lugano and are simultaneously part base network (length and height) was inside the networks a free positioning was of the global base network for AlpTransit strengthened at the portals of the tunnel chosen. The differences to the heights between Erstfeld and Lugano. AlpTransit and at the access galleries. This resulted from LN02 were less than 3 mm. Gotthard AG and COGESUD initiated the in the definitive form of the portal net- The planimetric densification followed in complex determining works for this networks (with high accuracy, for the stak- 2007 and 2008. Portal and construction work in the middle of the 1990s. Due to ing out of the tunnel) and the construc- site networks were established in Camor- the high requirements of these works, the tion networks (low requirements for the ino, Sigirino, and Vezia. They were then Swiss Federal Institute of Technology needs of the construction sites outside the integrated into the base network using Zurich (ETHZ) was involved as consultant tunnel). In those networks the sight line GNSS and terrestrial measurements. in a first phase. Later, combined measur- between the control points and the re- ing campaigns with GPS receivers and mote target points have to be kept free, Portal network Sigirino tachymeters were done. During the sub- which does not happen as a matter of From the Sigirino access tunnel, impor- sequent calculations, several variants course at such complex building sites. A tant parts of the base tunnel were staked were compared in order to obtain a ho- geologist previously assessed the stability out and excavated, which makes this por- mogenous and reliable geodetic base net- of the zones, in which the new control tal particularly important. The base con- work. The inner accuracy was ± 1 cm. points are set. trol network had already been partially At the end of 2005 the height control net- consolidated in relation to the staking out works for the construction sites were of the Sigirino exploratory tunnel, but for ReteSUD altezze complemented with subsequent level- the new main access gallery a few im- (South network altitude) lings. On the basis of a few height con- portant additions were necessary. Four In connection with the construction of the trol points of the national levelling net- new control points were added, amongst Ceneri Base Tunnel it was necessary to es- work, new control points were fixed in them the main portal pillar on the exten- tablish a special height control network the rock closest to the portals. On the sec- sion of the access gallery axis. Further- for the levelling underground and on the tion between Biasca and Lugano, a total more, a reference route was installed for surface. The Swiss Federal Office of of 42 new height control points were in- the gyro, which will later be useful dur- Topography (swisstopo) was assigned this stalled. The national levelling points were ing the stakeout controls in the tunnel for preparatory task. The factors influencing used as bearing points. To avoid tension the independent orientation controls. the theoretical deviations at the moment This reference route is 500 m long and in- of connection of the tunnel advances, es- cludes two pillars in the southern section pecially the gravimetric influence and the of the portal. influence of possible constraints between the height control points of the LN02 height reference framework had to be de- Portal network Camorino/Vigana termined. The conclusion of the swisstopo According to the work plans, only a few report showed that the influences com- hundred tunnel metres are excavated pensate themselves to a great extent, so from the Camorino portal. Depending on that the theoretical error is negligible. Us- Fig 3: Diagram of the main traverse. the other tunnel excavations, an optimal

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Fig. 5 Monitoring on the building sites. Fig. 6 Vezia preliminary cut. extension of 2 km in the southern direc- laps locally and temporally with the con- tees that the correct drive direction is tion is possible. struction of the road tunnel Vedeggio – maintained. As the contractor’s mandat- In Camorino, three new surveying pillars Cassarate. This situation requires a great ed surveying consortium, COGESUD has were prepared. These are situated on the coordination effort for all parties involved, to assure that the tunnel drives are joined mountain flank above the portals and are including those responsible for the sur- with a tolerance within the centimetre fixed to the rock. This slope is the only ge- veying. range at the point where the project en- ologically stable zone in the region. The gineers have planned it. At the moment new control points are a good basis for of the breakthrough, the maximum ad- the determination of the portal points on Staking-out of the main missible error is 25 cm. The main control the Magadino plain. Because the Maga- control points in the points in the tunnel are secured about dino plain consists of alluvial soil, this re- every 200 m with special bolts. Shafts with gion is subjected to subsidence and can- tunnel covers capable of handling traffic secure not be considered stable. Therefore, the The staking-out of the underground main the bolts. At the tunnel walls, securing portal points have to be newly determined control points is the most challenging and points are fixed which serve to control the for each new operation. at the same time the most fascinating of stability of the main points. The heights COGESUD’s tasks (Fig. 2). All work by con- are determined by levelling on the basis Portal network Vezia struction companies involved are based of the vertical control points of the por- The Vezia reverse-drive consists of a Tag- on those points. This procedure guaran- tal network. bautunnel (cut-and-cover tunnel) and a tunnel that is excavated conventionally in the rock. The whole section is 500 m long. The staking out of the tunnel in the rock is done from the preliminary cut, which has been carried out before. The cut-and- cover tunnel will be created only later on in the preliminary section. The external situation does not leave free space for creating a stable and secure portal network. A control point was created on the only existing rock outcrop. It is situated to the north of the portal along the SBB railway line. The main portal pillar was built relatively far from it on a meadow in the extension of the new tunnel axis in the direction of Lugano. The difficulty with this construction site is the fact that it over- Fig. 7 Three-dimensional visualization of the Sigirino landfill site.

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The determination of planimetric position tion profile or tunnel lining controls are the construction site. In spite of this diffi- is done by measuring a complex traverse performed. Proceeding from the coordi- cult situation, the project engineer’s ac- with forced centering (Fig. 3). The mea- nates of the known main points, the pro- curacy requirements to detect possible surements on all underground points files are measured without reflectors in movements of the monitoring points were performed several times during dif- accordance with the demands of the pro- were very high (simple standard deviation ferent campaigns in order to obtain the ject management. The measured profiles for the determination of the points: ± 1–2 required redundancy and to minimize the are analyzed with the appropriate soft- mm). An appropriate monitoring system error risk due to negative influences. The ware and compared to the reference pro- was created by adapting the densification global traverse begins at the main portal files defined by the project engineer (Fig. of the construction network and using a pillar of the corresponding portal net- 4). complex configuration of control points work. From this station all points of the It is thus possible for the project man- and measuring stations (which had to be portal network, as well as the first points agement to control the subcontractor’s newly determined at each intervention). of the underground network, are mea- compliance with the excavation accuracy The measurements at the beginning of sured to obtain the best possible connec- and to quantify the necessary volumes for the excavation were carried out every fort- tion between the exterior and the under- the concrete lining. night, but the rhythm has slowed down ground networks. In the tunnel network, in the meantime to quarterly control mea- there is no possibility to directly control surements. the orientation on the basis of exterior Monitoring of construction Another example of complex monitoring points of the south portal (ReteSUD), and Another important task of COGESUD is on the Vezia construction site is the an- all coordinates are based on the accura- the stability monitoring of the construc- chored pile wall situated about 100 m cy and reliability of the underground mea- tion outside the tunnel situated within the south of the tunnel portal. Because the surements. Many different rules help to influence range of the Ceneri Base Tun- SBB railway lines, which are in constant avoid possible negative influences. Often nel construction site. The objects to be operation, run on both sides of the moun- there are also very simple measurements monitored include existing buildings or tain, it is important to monitor the stabil- such as the double reading of the height buildings under construction in the sen- ity of this construction. Therefore, tachy- of an instrument or taking into account sitive zones of the project for which an metric measurements are performed pro- the necessary acclimatization time for the assessment of the current state for the fu- ceeding from the control points of the instruments in the case of temperature ture («prove a futura memoria» (assess- portal network. Every fortnight, COGE- changes. Every detail is important and has ment)) has been established. Amongst the SUD transmits the movements of a few to be recorded! chosen methods for these measurements selected points from the wall to the pro- In the calculation phase, the inner accu- are precise measuring procedures to as- ject engineers. The required accuracy for racy of the performed measurements has sess the current situation and the devel- the determination of the coordinates is to be assessed with a free adjustment. In opments over time. analogous to the one for the points of the rare cases and only on the basis of clear Aside from the existing objects, a great nearby preliminary cut. indications, conflicting measurements are number of new objects, such as walls, eliminated. In consequence, it has to be viaducts or other construction, which are Tunnel stakeout verified if the stochastic model, which built in connection with the base tunnel monitoring and special contains all a priori accuracies (depend- in the portal sector or along the railway ing on the instruments used and the mea- lines, have to be constantly monitored measurement techniques suring conditions), is confirmed. During (Fig. 5). Of these objects, the preliminary In its role as commissioned surveying con- the following global adjustment, in which Vezia cut (Fig. 6) can be mentioned as an sortium for AlpTransit Gotthard AG, CO- the new measurements are combined example. The elaboration of this moni- GESUD also has the task to control with all previous measurements, further toring project was challenging due to the whether all structures are built in the right parameters are taken into consideration, whole environment that had to be con- position and with the required tolerances. such as deviations from the vertical, geoid sidered potentially unstable (two big con- The project engineers have previously undulations, and distance reduction on struction sites in progress). Therefore, the fixed these factors. This means that height the basis of the Swiss map projection. localization of stable points posed a cer- and position of all structures built on the tain number of problems. In addition, sev- site have to be monitored regularly. The Excavation profile eral factors were hindering numerous local construction management coordi- sight lines. Those factors include the rel- nates these interventions, and plays an monitoring atively deep excavation (more than 20 m), important role as intermediary between In combination with the stakeout controls the curvature of the preliminary cut, as construction companies, project engi- of the main points in the tunnel, excava- well as the infrastructure and activities of neers, and COGESUD.

72 AlpTransit Gotthard

Members of the COGESUD consortium • Gisi e Bernasconi ingegneria e misurazioni SA Via Lugano 2a, 6924 Sorengo • Studio Meier SA Via Architetto Frizzi 26, 6648 Minusio Fig 8. Laserscan of the Vezia prelimi- • Studio d’ingegneria Antonio Barudoni nary cut. Via San Gottardo 20, 6600 Muralto • Studio d’ingegneria Antonio Bottani As the work was progressing, the survey- Via Stazione 7, 6987 Caslano ing specialists also had to accomplish very • Studio d’ingegneria Maderni-Capezzoli-Forrer Sagl special tasks, such as the elaboration of a Via San Salvatore 3, 6900 Massagno 3D-model of the Sigirino excavation material storage facility. On the basis of this model, a virtual film has been realized to Characteristics of the consortium show the situation at the end of the ex- • experienced specialists cavation work (Fig. 7). In addition, laser 12 engineers / 40 technical personnel / 8 staff members in administration scanning has been used in the «prove a • a full range of surveying services futura memoria» (assessment) in order to classic geodetic surveying, photogrammetry, terrestrial laser scanning document the state of the road geome- • fast availability and flexibility try and surfaces or, in the case of the Vezia ca. 150 operations (5000 hours) / year preliminary cut, to precisely determine the excavated volumes and to calculate the Contractual tasks cross sections (Fig. 8). • Provision of the required geodetic and topographical base data for Finally, the monitoring works in connec- the project planning and the construction of the Base Tunnel and the tion with the track lying in the tunnel adjoining buildings. should not be forgotten. This task still lies • Control that all planned buildings are constructed at the right place and in the future, but it will be another im- with the required accuracy. portant challenge in the project. All stake- • Detection and monitoring of potential deformations of the terrain and out and monitoring tasks in relation to the other affected objects, before, during and after the implementation of the installation of the railway infrastructure work. (rails, etc.) will be based on rail benchmarks, which will have to be determined Key activities with sub-millimetre accuracy. The rail benchmarks will later be used by the SBB • elaboration of the control networks for the maintenance works of the new Base network / portal networks / site networks railway line, on which the trains will run • construction companies’ stakeout controls for the constructions outside at over 200 km per hour! the tunnel and for the installation of the railway infrastructure • «Prove a futura memoria» (assessment) and monitoring of buildings and adjoining constructions Levelling / tachometric measurements / photographic data • staking out of expropriated surfaces and elaboration of construction Cristiano Bernasconi profiles for the projects outside the tunnel and for the public in-spection ing. dipl. ETH • special recording techniques for the project engineers Capo progetto topographic models / laser scanning / photogrammetric Analysis / COGESUD orthophotos Via Lugano 2a CH-6924 Sorengo

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points from the existing SBB railway em- Geomonitoring at the bankment, including the bridge, are also controlled during the same measuring North Portal of the Ceneri Base campaign. The measuring interval is flexible and adapted to the construction ac- Tunnel tivities, with the normal interval being every two weeks. These measurements The crossing beneath the A2 motorway is one of the important challenges in the nor- make it possible to document the long- thern sector of the Ceneri base tunnel. Aside from manual measurements, an auto- term settlement behavior over a large matic monitoring system constitutes the centerpiece of the monitoring for the A2 du- area. ring construction of the crossing. Throughout the two years of excavation, the monitoring system guaranteed the safety of the transit traffic on the A2 motorway. Automatic monitoring of the A2 The network based DC3 monitoring system is used to monitor the A2 railway low. Both companies have their head- crossing. This system registers relevant de- Th. Heiniger quarters in Regensdorf and already mon- formations in the area of the motorway itor the surroundings of the three dams and ensures safe operation of Switzer- located above the Gotthard Base Tunnel. land’s most important north-south con- North of the Ceneri, the planned NRLA nection with an automatic alarm system railway line climbs over a viaduct in the Manual monitoring when limit values are exceeded. In the Magadino alluvial plain to the height of The subsidence of the plain is periodical- area of two planned viaduct pillars in the the tunnel portal. The portal is situated ly controlled at over 110 points. At the Magadino plain, subsidence and water directly under the most important north- beginning of the fill, settlement level level measurements were connected to south transit road, the A2 motorway. The points were installed, which are adjusted the monitoring system in order to control alluvial plain is unavoidably affected by according to the growth of the embank- the settling behavior, during the preload, the train path construction and had al- ment. The measurements of these level in different depths up to 60 m. ready caused subsidence of up to 1.2 m points are performed geodetically using during different building projects in the total stations with regard to a higher-lev- Geodetic monitoring on the surface past. el reference framework. The maximum Forty-eight prisms have been installed on To guard against the expected settle- subsidence in this area is 90 cm, which the slopes and in the area of the project- ments, prior to work starting on the tun- corresponds to the accuracy established ed portal along the A2 motorway. These nel, the whole plain was loaded with ex- by the project engineer. In addition, the are measured every hour with two Leica cavation material from the Gotthard Base Tunnel in the area of the future railway path. In order to verify the consequences of the filling and to guarantee the safety of the A2 motorway during the crossing excavation through the Ceneri Base Tun- nel, it was decided to monitor the plain focusing on the A2 motorway crossing. The crossing of the A2 is situated in the first 50 m of the tunnel in the excavation material of the motorway embankment..

Lot704: Monitorraggio sedimenti A call for tender was published for monitoring as a separate lot. The IG Ceneri- Monitor with Amberg Technologies as lead-management company, together with BSF Swissphoto, obtained the con- Fig.1: Vigana: View of the Vigana north portal, over which the A2 passes – one tract to monitor the areas described be- of the two main traffic axes through Switzerland.

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Fig. 2: Survey pillar: Automatic monitoring along the A2 motorway – the monitoring system detects movements to a predetermined sensitivity of 3 mm.

TCA 1800 type total stations.. The col- • 2 uphill borings with 5 piezometer sen- water-bearing strata of the dam body. The lected data are used to monitor defor- sors each total stations measure the absolute shifts mations at the surface. This system, which The linked horizontal inclinometers mea- and subsidence of the boreholes. Thus, also covers the long-term monitoring of sure subsidence, and the vertical biaxial the results of the borehole measurements the dam body in particular, detects move- inclinometers measure transverse move- can be more adequately interpreted and ments with a predetermined sensitivity of ments in two axes. The elongation sen- compared with geodetic measurements. 3 mm, which puts a high demand on the sors measure shifts along the vertical stability of the system. The results of the boreholes and, hence, the settlements un- Analysis long-term monitoring indicate that under derground. Piezometer measurements The data of the automatic measurements good weather conditions these require- show the water pressure in the different are directly analysed and managed in the ments are met. In order to monitor the long-term stability of the fixed points, four GPS points have been added.

Underground geodetic monitoring In case of an unexpected event, total stations are unsuitable to detect movements as quickly as possible. These movements are therefore recorded with a dense network of geotechnical sensors at intervals of about 3 minutes. The sensors were installed in up to 50 m long horizontal boreholes between 4 and 8 m under the road surface. At the valley side border of the dam body 30 m deep borings were equipped with sensors.

The following sensors were used: • 4 horizontal borings with 70 interlinked uniaxial inclinometers • 6 vertical borings with 75 interlinked biaxial inclinometers • 2 vertical borings with 3 long measure- Fig. 3: GEOvis: With the web interface GEOvis all measuring data can be in- ment sensors each teractively consulted at any time.

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system on site. This provides an automatic Conclusion it almost impossible to see the prisms. Of- graph generation at each measurement ten we had to face the destruction of the process. The graphs are uploaded to the The automatic measurements were start- measuring points due to accidents on the GEOvis web-based data visualization por- ed about one year prior to the beginning motorway, construction work, and van- tal of Amberg Technologies at predefined of the tunnel excavation. This is necessary dalism. intervals. The project managers are able in monitoring projects of such complexi- In conclusion, it can be stated that the to consult the updated graphs anytime ty in order to gain experience with the sys- chosen measuring and alarm concept has and to acess archived data as well. The tem and to become familiar with the be- proved to be totally efficient, although the manual data are analyzed within a day, havior of the system in different environ- 24-hour on-call duty was a great burden and the diagrams are also provided in the mental conditions. In November 2008 the for the IG Ceneri-Monitor personnel. GEOvis system. alarm was set on «high» and the critical Therefore, not only the people involved in phase of the underground crossing was the project but also the monitoring spe- Alarm successfully mastered by mid-2012. The cialists of IG Ceneri-Monitor are relieved The project engineer has set two-stage measured subsidence of max. 14 cm lie that the A2 motorway crossing has been limit values for maximum allowable move- within the range established by the pro- successfully completed and are looking ments. If after a measurement cycle, an ject engineer. Thanks to intelligent inter- forward to a future without mobile excess of those pre-set values is detected, nal system controls, false alarms could be phones at their bedsides. the monitoring system automatically avoided with two exceptions. While the alerts the responsible persons by SMS and geotechnical sensors were not widely in- over the telephone by voice message. The fluenced by environmental conditions, recipients are forced to actively confirm thus having no affect on the functioning the receipt of the messages; otherwise the of the alarm system, the geodetic mea- messages are forwarded to their deputies. surements posed a certain number of In case of an alarm, the newest graphs challenges. The quick growth of the veg- Thomas Heiniger are immediately made available in the etation and the heavy rainwater spray de- Amberg Technologies AG GEOvis system and are at the disposal of manded a continuing effort to grub-up Trockenloostrasse 21 the responsible persons for situation the ground around the sight lines and CH 8105 Regensdorf-Watt analysis. clean the prisms. Very deep snow made [email protected]

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With the help of pre-analyses calculations Astro-geodetic measurements of geodetic networks, the Gotthard Base Tunnel (VI_GBT) surveying consortium of vertical deflections and was assigned all the surveying work by the main contractor and they had deter- azimuths for ALPTRANSIT mined the average excavation errors at the different meeting points to be 10 cm Before beginning work at this century’s most complex construction site, the Gotthard (1 sigma) on the lateral component and Base Tunnel project required an extensive feasibility study in addition to a study con- 5 cm on the altimetric component. More- cerning the accuracy of the surveying work. In order to provide and increase the ac- over, the horizontal coordinates had to be curacy of the survey work, all possible and independent measurement techniques had determined with an external accuracy of to be considered. More specifically, the systematic effects of the gravitational field, 25 cm (maximum permissible error) and which affect observations depending on the vertical such as tacheometric, gyroscop- the altitudes with an accuracy of 12.5 cm ic or levelling measurements, needed to be known or to be determined with the high- (Haag et al. 1996, Stengele 2007). These est precision. This translated into the need for precise knowledge of the geoid, the accuracy and reliability requirements can deflections of the vertical, and the vertical acceleration of gravity g. This article de- be met only thanks to independent meth- scribes the astrogeodetic control surveys that were carried out by ETH Zürich in the ods such as, e.g., gyroscopic measure- summer of 2005 on behalf of the VI-GBT surveying consortium, in order to verify the ments. Moreover, gyroscopic measure- values of the corrections applied to the gyroscopic measurements. Moreover, the ments on calibration bases at the portals CHGeo98 geoid model used in this project had to be validated in order to verify could be controlled independently and ef- whether it provided the desired accuracy or if new vertical deflection surveys were ficiently with measurements of the astro- necessary in combination with the new CHGeo2004 geoid model. 04. nomic azimuth and vertical deflection, which increases the reliability of the global surveying work. In the context of underground construction, such as the Gotthard Base Tunnel, the effect of the earth’s gravity field is of all error sources and their effect on the fi- utmost importance for the measure- Beat Bürki and Sébastien Guillaume nal accuracy have to be studied and added ments. The visible impression of the grav- to the surveyor’s task lists. ity field will appear in the form of a ver- The building of a structure such as the tical deflection, which will be expressed 1. Introduction Gotthard Base Tunnel, at the unprece- by a local deviation from the normal range dented length of 57 km, poses a major at the reference ellipsoid. This deflection The successful management of an ambi- challenge to surveyors. The division of is normally described by two components: tious project, such as the new transalpine work into five segments resulted in an ac- north-south and east-west rail link (NEAT) with the Gotthard Base celeration of the construction, as the max- Tunnel, depends on many different fac- imum segment was 16.8 km (Faido-Se- north-south component: ξ = Φ − j (1) tors. In addition to technical and financial drun construction site). In spite of this sim- east-west component: questions, as well as the parliamentary plification, each segment was a great η = (Λ−λ)⋅cosj (2) obstacle course, a tremendous number of challenge regarding the quality of the questions concerning the technical, eco- measurements. Due to complications in- with Φ,Λ = astronomic latitude and lon- nomical, and ecological conduct of the volving environmental conditions on the gitude defined by astro-geodetic work had to be resolved. To achieve this, construction sites, the preliminary calcu- methods (for example, using a an army of planners, engineers, geolo- lations of the directions for the tunnel bor- zenith camera) or calculated on the gists, hydrologists, traffic and energy ex- ing machines (TBM) had to be performed basis of reference points and digital perts, mining engineering experts, legal with utmost care and had to take into ac- mass models. experts, and last but not least geomatic count all possible error sources [Haag et with j,λ = geodetic latitude and longi- engineers dealt with a broad spectrum of al. 1996, Stengele 2007, Schätti and Ryf tude (ellipsoidal) defined by GNSS or problems arising from such a project. In 2007]. Reporting the portal network di- from Cartesian coordinates convert- terms of survey techniques, the challenge rections on the front of the tunnel exca- ed on the reference ellipsoid. lies in meeting the accuracy requirements vation using classical direction measure- needed by the prime contractor. In order ments resulted in polygonal and super- The obliquity of the physical vertical in re- to satisfy these mandatory requirements, imposed lines. lation to the mathematical vertical sys-

77 AlpTransit Gotthard

tematically influences the angular obser- These values show that the first term is els. The attainable accuracy depends on vations because the vertical axis of the in- significantly higher than the precision of the quality and the density of the gravity strument is also subjected to the same the measurements. Consequently, it is es- field measuring station network. In obliquity. A direction correction, dr, sential to take this into account to reduce Switzerland, there is a network of 650 ver- caused by the vertical deflection, depends the gyroscopic azimuths measured on the tical deflection observation stations used on the azimuth α, the line of sight, and reference ellipsoid of the Swiss reference for the determination of the geoid. This the zenithal axis z. system in order to compare them to the is the basis for the interpolation of the azimuths of the basic control network de- vertical deflections on a given point on dr = –(ξ⋅sinα − η⋅cosα)⋅cot(z) (3) termined by GNSS. The second term can the terrain with accuracy between 0.8’’ be neglected due to the fact that it is sig- and 1.0’’. In this project, vertical deflec- Laplace's equation describes the differ- nificantly smaller than the precision of the tions have been calculated along the tun- ence, dA, between the astronomical and measurements. nel axis with the help of the CHGeo98 ellipsoidal azimuths: In theory, there are other corrections to geoid model. consider. The graphic representation of Fig. 1 shows dA = - η⋅tanj –(ξ⋅sinα − η⋅cosα)⋅cot(z) the vertical deflections as well as the po- (4) Instrument-independent corrections sition of the astro-geodetic stations of the • Current position of the earth’s axis of ETHZ in the project sector. In the past, the deviation of the main ax- rotation Ǟ reduction to the average val- A profile of the vertical deflections based is of the instrument was not adjustable ue of the position of the pole. CIO Pole on geoid model calculations along the due to the positioning of the instrument. (Conventional International Origin) tunnel axis is shown in Fig. 2. As a result, it was impossible to distin- • Convergence of meridians Ǟ reduction guish it from the systematic influence of in the north of the map 2.2 Geoid-ellipsoid separation the vertical deflection. Modern instru- • Altitude of the sight line over the sea The planimetric determination of control ments, such as tachymeters and total sta- (obliquity of the ellipsoid reference at points is easily done by referring to the tions, which are equipped with dual-axis the sight line in relation to the ellipsoid mathematically perfectly described sur- compensation (tilt measurements), can reference at the measuring point) face of the Bessel ellipsoid regarding the measure the deviation of the principal ax- • Reduction of the direction ellipsoid- geodetic datum of the Swiss national sur- is and calculate and correct its measure- sphere-plan (geodetic line-big circle- vey. For the determination of heights, the ments (provided that the compensator is straight line in the projection plan) reference surface is not mathematical but activated). Therefore, only the vertical de- physical–the geoid. In fact, the geoid can- flection influences the measurements ac- Instrumental corrections of the not be as easily represented in a model as cording to the formula (4). gyroscope an ellipsoid because it is dependent on When reducing the azimuths measured • Correction of point zero (calibration) the distribution of land masses and thereby gyroscope by the components ξ and • Correction of drift effect (temporary before closely correlated with the topogra- η of the vertical deflection, the curvature havior of the calibration value). phy. For this reason, planimetric and alti- of the gravity line must also be taken in- • Accounting of temperature variations metric determinations in principle are to account. The results of a comparison In practical terms, this means that at the separated as in the LTOP adjustment soft- at the Sedrun vertical shaft, for example, construction site the surveyor or the GIS ware. In the AlpTransit project, the LN02 showed that the vertical deflection over specialist responsible for the measure- altimetric reference frame has been used the 800 m between the top and the bot- ments has to regularly perform control and new rigorous LN95 orthometric tom of the shaft varies between –6.1 cc measurements under good conditions heights have been taken into account. (-0.61 mgon) in the north-south direction and absolutely needs to know the local The corresponding reference surface re- and –3.2 cc (–0.32 mgon) in the east-west gravity field. sults from the CHGeo98geoid model. Fig. direction. After an accurate analysis ac- 3 shows the profile of the geoid along the cording to Laplace's equation, these val- 2. The gravity field in the tunnel axis. ues applied to the tunnel height result in region of the Gotthard the following corrections: Base Tunnel 3. The astro-geodetic First term: from –49 cc to +20 cc control measures of the 2.1 Vertical deflections Second term: from –0.11 cc to +0.05 cc Vertical deflections can be observed di- ETH Zurich (for lines of sight at 0 degrees azimuth), rectly at the site (i.e., with the help of a The Geodesy and Geodynamics Labora- and from –0.35 cc to +0.11 cc (for lines zenith camera) or on the basis of calcula- tory (GGL), of the ETHZ through the con- of sight at 90 degrees azimuth). tions integrating mass and terrain mod- sortium «Pesanteur suisse», has been giv-

78 AlpTransit Gotthard

Fig. 1: Variations of vertical deflection at the altitude of the Gotthard Base Tunnel. The yellow stars represent the positions of the astro-geodetic measuring stations by zenith camera and the blue arrows show the measured astronomic azimuth (3 columns). en the mission by VI-GBT (renamed ATG consists of a Leica Geosystems TCA 1800 priate software (see Fig. 2). The terrain géomatique since September 1st, 2010) total station equipped with a prism, a spe- calculator contains a star catalogue. It to validate and carry out an independent cial GPS receiver for time acquisition with steers the motorized theodolite and cen- control of the correction values for the gy- a manual switch, an interface device, and tralizes data processing by providing real- roscopic measurements and the vertical a terrain calculator along with the appro- time accuracy information on the terrain. deflection. The assignment consisted of measurements of vertical deflections and astro-geodesic azimuths at the calibration networks of the Amsteg, Bodio, Erstfeld, Faido, and Sedrun portals (see Fig. 1).

3.1 Azimuth survey Students David Grimm, Florian Buol and Sébastien Guillaume under the supervision of Dr B. Bürki and engineer A. Ryf have done the astro-geodetic measurements of the azimuths in the context of a diploma course at ETHZ. In order to achieve this, the AZIMUT real time measurement developed by GGL had to be Fig. 2: Variations of the vertical deflection in its components ξ and η along the used. This automatic measuring system tunnel axis.

79 AlpTransit Gotthard

Fig. 3: Comparison of CHGeo98 and CHGeo2004 solutions. Although the new solution shows undulations over 7 cm, the effects on the height differences at the intersection points remain acceptable.

After careful verification of the different Leibniz University in Hannover made it 3.4 Survey works mires (targets for astro-geodetic mea- possible to perform a reciprocal control of In theory, the measurements of the verti- surements of the azimuths), the standard the gravity directions according to the re- cal deflections should be done on geo- circular prisms of the non-illuminated to- quests of the contractor. detic pillars. This of course being impos- tal station, and with the automatic func- sible, the observations have to be done in tion (ATR), have been used. 3.3 The measuring principle of as close proximity as possible. Due to dif- During the measurements, the ATR zenith cameras ficult and partially impossible access, the method has proven its reliability. The tar- Zenith cameras, such as those developed cameras had to be mounted relatively far get search was not easy and was done by the GGL of ETHZ and the Institut für from the theoretical measuring points. using a strong flashlight to scan the ap- Erdmessung at Hannover University (IfE), proximate direction of the target. Subse- are used for the very precise determina- quently, the measurements were per- tion of the physical direction of the plumb formed in a semi-automatic way with the line using the photographic measurement AZIMUT system, which records the posi- of the stellar directions. The stellar field tion of the targets. This procedure sim- measured by a CCD camera is compared plifies performing the measurements and to the reference stellar field. This refer- avoids reading errors. ence field is calculated from the position All azimuth measurements were per- of the station, the exposure time, and a formed in the two positions of the lens stellar catalogue (e.g., Tycho-2 or UCAC). and, depending on the metrological con- The DIADEM system, in addition to ex- ditions, measured up to five times. The re- cellent optics and an appropriate CCD sults of the five azimuth measurements camera, includes three pairs of highly sen- resulted in an internal accuracy between sitive inclinometers mounted in pairs at 0.1 and 0.8 arc-seconds (0.03 and 0.24 right angles. mgon), which can be qualified as very After introducing the inclination values fil- good given the nominal precision of the tered in real-time and numerous correc- TCA 1800 of 1’’ respectively 0.3 mgon as tions, the projection of the camera’s ro- indicated by the manufacturer. tation axis in the interpolated stellar field gives the physical direction of the plumb 3.2 Vertical deflection survey line expressed by the astronomical lati- The vertical deflections have been mea- tude and longitude. Then, using the for- sured with the help of two very analogue mulas (1) and (2), the components of the Fig. 4: Geomatic engineering student zenith cameras during a common mea- vertical deflection ξ and η are deter- and co-author of the present article S. suring campaign. The DIADEM (Digital As- mined. With the new version of the zenith Guillaume, measuring an astro-geo- tronomical Deflection Measuring) system camera, an accuracy of 0.05 arc-seconds detic azimuth between terrestrial of ETHZ and the TZK2-D (transportable can be obtained on the components of mire and the polar star (alpha Ursae ZenitKamera2 -Digital Version) system of the deflection. Minoris).

80 AlpTransit Gotthard

This unusual installation, however, was taking into account all the effects that AlpTransit project and the new not problematic because the determina- can be modeled, such as proper move- CHGeo2004 model improved by the new tion of the ellipsoid coordinates by RTK- ment, precession, nutation, parallax, measurements are small (see Fig. 5), so GNSS measurements at the camera’s real optical aberration and the movement of that no significant influences are to be ex- point is easily done. Moreover, it is possi- the poles. pected. ble to transpose the deflection values • The exactitude of the calculations of the from the real to the theoretical measur- astronomic azimuths based on appar- 5.2 Comparison of the vertical ing point (from the eccentric point to the ent positions. deflections center of the pillar) by using mass models. The controls of the apparent positions car- The differences of the vertical deflections The first series of observations with the ried out at the Astronomical Institute of are shown in Table 3. two-camera systems were performed on the University of Bern [Ploner, 2005] as This comparison shows that the July 13, 2005 at the Amsteg, Bodio, Erst- well as by Hirt, [2005] were perfectly con- CHGeo98 geoid was able to meet the ac- feld and Faido stations (see Fig. 4). At each cordant with the values obtained by curacy requirements of AlpTransit. station, the vertical deflection had been AZIMUT. The results were therefore con- The comparisons of CHGeo2004 in Fig. 6 determined on the basis of between 40 sidered reliable and handed over to the remain in the range of measuring errors and 80 solutions. During a second obser- contractor (see Table 2). or even below. vation night on July 19, 2005, 130 solutions had been observed during 6 hours 5. Comparison of the 6. Conclusions by using the DIADEM system. This long CHGeo98 and the measuring period was due to the bad The results of the astro-geodetic control weather conditions, as the cloud cover CHGeo2004 geoids measurements have provided the follow- made the astronomical observations dif- To control and ensure the adequacy of the ing conclusions: ficult. geoid–ellipsoid separation and the verti- 1) Not only the azimuths but also the cal deflection used to date (CHGeo98), a measurements of vertical deflections comparative calculation with the new were carried out with great precision 4. Survey results geoid (CHGeo2004), including the new and the results are reliable. They meet 4.1 Vertical deflection vertical deflections, could be carried out the high accuracy requirements im- The results of the measurements of the by U. Marti from swisstopo (see Table 1). posed by the contractor. plumb line’s direction can be described in 2) The astronomic azimuths do not differ the form of a simple and global table. 5.1 Comparison of the geoid- significantly from those obtained from Table 1 shows the directions of the plumb ellipsoid separation GPS coordinates [Ryf 2007]. line Φ at the center of the observation pil- The differences calculated between the 3) The astronomic azimuths were used as lars as well as the deflections deducted CHGeo98 reference model used in the observations to calculate overall com- from them by using the formulas (1) and (2). The accuracy of each component can be estimated at σ(ξ,η) = 0.1’’

4.2 Azimuths The automatic data processing on the site with the help of the AZIMUT program made it possible to proceed to an un- problematic elimination of aberrant values. Therefore, major measurement errors are virtually impossible. To ensure the required reliability the following aspects have been examined at the end of the measuring process. • The calculation exactitude of the series of azimuth measurements on the basis of observations derived from the AZ- IMUT system. • The exactitude of calculations of the ap- Fig. 5: The two zenith camera systems of the Leibnitz University of Hannover parent positions (α, δ) of the pole star (left) and the ETHZ (right) during the survey at the Erstfeld portal pillar.

81 AlpTransit Gotthard

pensation in LTOP to determine the co- Station Result A posteriori ordinates of the basis network and en- accuracy vision a small rotation of the north portal network, which, however, remains Bodio pillar 12735901 final azimuth 12735901 → σ(Az) = 0.10“ well below the limit of statistical sig- 12735902 = 320° 40’ 26.55” nificance. 4) The differences in the gyroscopic az- Faido pillar 12525901 final azimuth 12525901→ σ(Az) = 0.21“ imuths are tolerable and have no ef- 12525902 = 111° 57’ 24.43” fect on the accuracy at the crossing Sedrun pillar 12122901 final azimuth 12122901→ points. σ(Az) = 0.41“ 5) The results of the measurements of ver- 12122930 = 244° 51’ 55.96” tical deflections combined with the Amsteg pillar 12124902 final azimuth 12734902 → σ(Az) = 0.40“ new CHGeo2004 geoid model vali- 11924910 = 356° 13’ 05.80” dates the CHGeo98 geoid model used for the project. Erstfeld pillar 11924903 final azimuth 11924903 → σ(Az) = 0.81“ In summary, we can say that astro-geo- 11924145 = 145° 40’ 10.17” detic measurements are important and useful to validate the reduction values of Table 2: Astronomic azimuths for the control of the gyroscopic measurements. Earth’s gravity field applied to the observations and for the improvement in relia- Deflection difference (CHGeo2004) – observed deflections bility of all measurements related to the (datum CH1903, northern part of the map) tunnel. difference CHGeo2004 model measurements CHGeo2004- References: measurements Bürki, B., M. Ganz, Ch. Hirt, U. Marti, A. Müller, PV Radogna, A. Schlatter, A. Wiget (2005): Station ξ calc. [’’] η calc [’’] ξ obs. [’’] η obs. [’’] dξ [’’] dη [’’] Astrogeodätische und gravimetrische Zu - Bodio pillar 3.66 13.19 3.67 13.64 –0.01 –0.45 satzmessungen für den Gotthard-Basistunnel. Faido pillar –5.37 9.10 –4.93 9.79 –0.44 –0.69 Vergleiche zwischen Astogeodätischen und gravimetrischen Messungen vom Sommer Erstfeld pillar 16.87 10.09 16.74 10.72 –0.13 –0.63 2005 mit modellbasierten Werten. Swisstopo- Amsteg pillar 18.53 –9.79 18.85 –9.15 –0.32 –0.64 Report 05–34. Sedrun pillar 1.24 4.37 2.25 4.41 –1.01 –0.04 Haag, R., A. Ryf & R. Stengele (1996): «Grund- lagenvermessung für extrem lange Tunnel am Table 3: Comparisons of the geoid solutions CHGeo98 and CHGeo2004 ac- Beispiel des Gotthard-Basis-Tunnels.» XII. In- cording to the vertical deflections. ternationalen Kurs für Ingenieurvermessung, Graz.

Vertical deflections in the datum CH1903 in relation of the North of the map

Station ξ ["] η ["] ξ [cc] η [cc] Bodio pillar 3.67 13.64 11.32 42.12 Faido pillar –4.93 9.79 –15.22 30.23 Erstfeld pillar 16.74 10.72 51.64 33.09 Amsteg pillar 18.85 –9.15 58.17 –28.24 Sedrun pillar 2.25 4.41 6.93 13.62

Table 1: 2005 measurements of the vertical deflections used to control the Fig. 5: The difference of the global vertical deflection between the CHGeo98 geoid solution and of the corrections and CHGeo2004 geoids remains within a narrow band of ± 1.7 cc (0.17 mgon) applied to the gyroscopic measure- proving that the CHGeo98 model has totally fulfilled the accuracy requirements of the NEAT project. ments.

82 AlpTransit Gotthard

Absteckung des Gotthard-Basis-Tunnels.» Geo matik Schweiz, Heft 06/2006. Schätti, I. und A. Ryf (2007): «AlpTransit Gott - hard-Basistunnel: Grundlagenvermessung, letzte Kontrollen vor dem ersten Durchschlag.» XV. Konferenz für Ingenieurvermessung, Graz. Stengele, R. & R. Haag (1998): «Geodätische Aspekte bei der Vermessung des 57 km lan- gen Gotthard-Basistunnels.» Messen in der Geotechnik 98, Mitteilung des Instituts für Grundbau und Bodenmechanik TU Braun- schweig, S. 301–312. Stengele, R. (2007): «Erster Hauptdurchschlag im Gotthard-Basistunnel: Tunnelvermessung in Theorie und Praxis». 15. Internationaler Kurs für Ingenieurvermessung. Graz. Zanini, M., R. Stengele & M. Plazibat (1993): Fig. 6: The difference of the global vertical deflection between the CHGeo98 «Kreiselazimute in Tunnelnetzen unter Einfluss and CHGeo2004 geoids remains within a narrow band of ± 1.7 cc (0.17 mgon) des Erdschwerefeldes», Berichte des Instituts proving that the CHGeo98 model has totally fulfilled the accuracy require- für Geodäsie und Photogrammetrie der ETH ments. Zürich, Nr. 214.

Haag, R., F. Bräker & R. Stengele (1998): «A Hirt, C. und Bürki, B. (2002): «The Digital 57 km long Railway Tunnel through the Swiss Zenith Camera – A New High-Precision and Alps and its planned Survey.» Proc. XXI. Inter- Economic Astrogeodetic Observation System national Congress FIG Brighton, for Real-Time Measurement of Vertical De- rd Haag, R. & R. Stengele (1999): «Vermessungs - flections». Proc. of the 3 Meeting of the In- technische Grundlagen und Herausforderun- ternational Gravity and Geoid Commission of Beat Bürki und Sébastien Guillaume gen beim Projekt Alp-Transit-Gotthard-Basis- the International Association of Geodesy, ETH Zürich, Institut für Geodäsie und tunnel.» Moderne Sensorik für die Bauver- Thessaloniki (ed. I. Tziavos): pp. 161–166. Photogrammetrie messung, VDI-Gesellschaft Bautechnik, Be - Ploner, M. (2005): Communication person- CH-8093 Zürich richt 1454, S. 225–240. nelle. [email protected] Hirt, C. (2005): Communication personnelle. Schätti, I. (2006): «Herausforderungen bei der [email protected]

83 AlpTransit Gotthard

From potential theory to the subsidences at the Gotthard Pass

What began as a potentially harmless theoretical academic field test before the beginning of construction of the Gotthard Base Tunnel ended in 1997 with the surpri- sing discovery of massive subsidences at the Gotthard Pass. A short look back to how the search for confirmation of the potential theory led to a very different discovery.

forming crevasses (so-called Nacken- A. Geiger, A. Schlatter tälchen) on the mountainside, also emerge above Andermatt. There, at Stöckli – Lutersee, geodetic measure- What does the potential Fig. 1: Subsidence at the Gotthard pass theory have to do with a ments performed by the Institute for Geo- desy and Photogrammetry of the ETH between Wassen–Göschenen–Hos- tunnel? showed small vertical differential move- pental and Guspisbach; Original This question is seldomly asked as long ments of several tenths of a millimetre per graph from the first publication of the railway tunnels are built. Nevertheless, the year. P. Eckardt et al. (2/1983) describe press communiqué dated January answer to the question is particularly im- these distortions in an article in «Vermes- 22,1998 (Schneider, Schlatter 1998). portant in the context of the construction sung, Photogrammetrie, Kulturtechnik», of the currently longest railway tunnel, the predecessor journal of «Geomatik Haag from VI-GBT, swisstopo and IGP the Gotthard. Although the answer does Schweiz». The deformation problems (ETHZ), which focused on what addition- not look particularly scientific, it briefly arising shortly after the tunnel opening at al knowledge could be gained from fur- highlights a small side aspect of geodet- «Kilometre 4» of the road tunnel are pos- ther measurements. On the one hand, ic research. sibly due to this moving mechanism. there was the question of the correlation In the 1990s, anybody remotely interest- Above Sedrun, in the area of the Caschlé between surface and tunnel deforma- ed in geology knew that the Gotthard Alp, high above the planned Gotthard tions and, on the other hand, the poten- massif did not ultimately stand fixed and Base Tunnel, these postglacial disruptions tial-theory interest in the investigation of unchanging. It was part of the uplift of were also observed. They have been ge- a vertical levelling loop. The test site is ide- the Alps. After the works of F. Jeanrichard odetically surveyed repeatedly in the al because the surface levelling between and E. Gubler (consecutive directors at the 1990s by the Gotthard Base Tunnel Sur- the Hospental and Guspisbach ventilation the Federal Office of Topography swis- veying Consortium (VI-GBT) in the knowl- shafts run exactly above the levelling of stopo) and after the tireless geodetic-tec- edge that movements may occur. the tunnel. At the ends of the levelling tonic investigations by H.-G. Kahle (at that D. Schneider, the head of the former lines the «top and bottom heights» time professor of geodesy at the Swiss Geodetic Bases Section of swisstopo and can be directly linked by a vertical distance Federal Institute of Technology, ETH, and promoter of the integration of deforma- measurement. The length of the plumb president of the Swiss Geodetic Commis- tion theory findings in the national sur- line can therefore be directly measured, sion), it became clear that the Alps are lift- vey, developed a concept for repeated so to speak, in the earth's interior, at two ing up a few millimetres. In other words, measurements of the road tunnel level- points which are so close that the there are deformations of the solid ling, specifically in relation to deforma- connecting levellings are very accurate bedrock. tions. The measurements were performed and can be performed with reasonable Aside from the widespread tectonic by VIGBT and swisstopo during an inter- effort. Briefly, the site is ideal for geo- processes, local Late Quaternary distor- ruption in operations caused by mainte- detic testing and who can afford to ig- tions are apparent on the slopes of the nance work in June 1997. Lively discus- nore a geodetic laboratory with a tunnel Rhine-Rhone valley line. These differen- sions took place between the GBT sur- and two vertical shafts of 320 m and 530 tial shifts, clearly visible on the terrain and veying project manager, F. Bräker, and R. m long?

84 AlpTransit Gotthard

From the measurements to These discoveries prompted the supervi- 72, Schweizerische Geodätische Kommission, the great surprise sory authorities and the constructor to ini- 373 Schlatter, A., E. Gubler, B. Mattli, D. tiate extensive investigations coupled Schneider The cooperation of all involved parties and with the first geodetic zero-measure- (1997). Neues Landeshöhennetz LHN95: De- the additional financial help from the ments in the whole AlpTransit region. The formations-Analyse Gotthard. Untersuchun- Swiss Geodetic Commission and the Swiss zero-measurements aimed to document gen der Senkungserscheinungen im Bereich Academy of Sciences made it possible to the current state, which can be referred des Gotthard-Strassentunnels. Technischer Bericht 97-40, Bundesamt für Landestopogra- perform the measurements immediately. to later. Thus, wide-range levelling sur- phie, Wabern.Seiten. ISBN 978-3-908440-16- They had to coincide with the tunnel veys were performed by swisstopo over 1. maintenance. From September 23 to 25, the Furka, Oberalp and Lukmanier pass- Schneider, D. (1997). AlpTransit Gotthard-Ba- 1997, there were very few afternoon es and down to the Val Nalps. In the con- sistunnel: Deformationsmessungen im Gott - hours left to perform the distance mea- text of surveying and monitoring assign- hard-Strassentunnel (A2). Technischer Bericht surements in the vertical shafts using a ments, the deformations of the undercut 97–13, Bundesamt für Landestopographie, Kern Mekometer 5000. At the end of the dams had also to be monitored geodeti- Wabern. same month the levelling along the pass cally. With hindsight regarding the Zeuzi- Schneider, D., A. Schlatter (1998): RCM – road was done by swisstopo and VI-GBT. er case (dam deformations, for example Analyse Gotthard. Pressecommuniqué, L+T, The first analyses of the surveys from Hos- Bierdermann 1980) everybody agreed up- 22.1.1998. pental to Guspisbach (5 km long and 330 on a proactive, forward-oriented strategy Schneider, F. (1978). Nivellement und Schwere - m height difference) differed considerably for the geodetic monitoring measures. messungen am Gotthard. Bericht 17, Institut from the former pass levelling of 1970. The influence of rock drainages on the für Geodäsie und Photogrammetrie, ETH There were 8 cm of subsidence! An en- drilled rock in particular had to be viewed Zürich. tire world for a leveller. After further con- in a new light. Who has failed to look for Wiget, A., U. Marti und A. Schlatter (2010). trol measurements and analyses, it could something precise and found something Beiträge der Landesvermessung zum AlpTran- not be explained away: the rock between else entirely? Should we not seize the oc- sit Gotthard-Basistunnel, Geomatik Schweiz, Hospental and Guspisbach had sunk . In casion of the next long period of tunnel 12/2010. January 1998, this moving mountain re- closure to verify the potential theory sult was published in a swisstopo press again? Will there be further surprises? Alain Geiger communiqué (see Fig. 1 from Schneider, Institut für Geodäsie und Schlatter 1998). The authors talk about Photogrammetrie References: the most important bedrock subsidence ETH Zürich Biedermann, R. (1980). Ausserordentliches phenomenon ever observed in Switzer- Schafmattstrasse 34 Verhalten der Staumauer Zeuzier. Wasser, land. As a consequence, the rest of the Energie. Luft, 72. Jahrgang, Heft 7/8. CH-8093 Zürich Gotthard pass levelling was repeated from [email protected] Eckhardt, P., H. Funk, T. Labhart mit Beiträgen Guspisbach to Airolo. The analysis the lev- von W. Fischer und E. Gubler (1983). Post- elling data confirmed the already feared, glaziale Krustenbewegungen an der Rhein- Andreas Schlatter very worrying results. In the central sec- Rhone- Linie; Vermessung, Photogrammetrie, Bundesamt für Landestopografie tion of the alp excavation, there must have Kulturtechnik, 2/83. swisstopo been signs of subsidences. A summary of Schlatter, A. (2007). Das neue Landeshöhen- Seftigenstrasse 264 the subsidence (Schlatter, 2007) is shown netz der Schweiz LHN95. Geodätisch-geo- CH-3084 Bern-Wabern in Wiget et al., 2010. physikalische Arbeiten in der Schweiz, Band [email protected]

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Surveying work at the Lötschberg Base Tunnel after the final breakthrough

The Lötschberg Base Tunnel, together with the already existing Simplon tunnel, is the first high-speed north-south connection through the Alps. For all the specialists involved, the Lötschberg Base Tunnel project was a challenge. Surveying such a long tunnel also constituted a very demanding task. The article «Tunnelvermessung des BLS AlpTransit Lötschberg-Basistunnels» in the professional journal «Geomatik Schweiz» 11/2005 addresses the main issue of tunnel surveying up to the main breakthrough. Aside from a summary of the results after the final breakthrough, the present report explores the following three surveying tasks: error of breakthrough compensation, monitoring of the ballastless tracks, and installation of the structural monitoring.

structed simultaneously from five build- H.-U. Riesen ing sites. Aside from the two portal building sites Frutigen and Raron, there were Project description the intermediate headings of Mitholz, Fer- Fig. 1: Schematic representation of the den and Steg/Niedergesteln. The two different boring methods (green and The Lötschberg Base Tunnel leads from Rhone bridges at Raron as well as the cut- red: driving by drilling and blasting; Frutigen in the Kander valley (Bernese and-cover Engstlige tunnel at Frutigen blue: TBM). Oberland) to Raron in the Rhone valley were important outdoor constructions (Canton of Valais). It is 34.6 km long and (Fig.1). The total length of the excavated • ristag Ingenieure AG (formerly Riesen & is designed as a one track, two-tube rail- tubes and galleries amounts to 88.1 km. Stettler AG), Urtenen-Schönbühl way tunnel (separated by direction). For Eighty percent of the tunnel system was • BSAP Ingenieure und Berater, Brig-Glis financial reasons, the tunnel was con- excavated by drilling and blasting, the re- • Häberli + Toneatti AG, Spiez structed in various phases. In the first ex- maining 20% were driven using tunnel • Klaus Aufdenblatten Geomatik AG, Zer- pansion phase, the west Steg bypass with boring machines (Fig. 1). matt. the Niedergesteln portal as well as the According to the system option chosen, Specialists west tunnel from Ferden to Mitholz re- it was decided to build two parallel sin- To create and complement the above- main shell constructions. In the Mitholz- gle-track tunnels, which are linked to each ground base network, the Federal Office Frutigen section, only one tunnel tube has other every 330 m by galleries. This vari- of Topography swisstopo was called in as been excavated. The exploratory Kander- ant constitutes the optimum solution re- subcontractor. The Lötschberg Base Tun- tal tunnel built from 1994 to 1996 runs garding the criteria of construction (costs, nel layout was done completely within the parallel to this track. building time, environment), operation reference frame of the new LV95 (GPS) Construction work at the base tunnel (operational requirements, preservation national survey and on the basis of the tubes was initiated in 1999. The final and maintenance, aerodynamics and LHN95 national height network. breakthrough between the Cantons of thermodynamics), and safety (accep- Several institutes as subcontractors per- Valais and Berne, which concluded the ex- tance, risk). formed the gyroscopic measurements: cavation work, was celebrated on April • ETH Zürich, Institut für Geodäsie und 28, 2005. The interior work and the rail- Photogrammetrie (IGP-ETHZ) way infrastructure installation lasted un- Project participants • Universität der Bundeswehr München, til November 2006. The opening cere- Project surveyor Institut für Geodäsie (IfG), Deutschland mony and the handover to the operator In a two-level bidding procedure, the en- BLS AG took place on June 15, 2007. In gineering association Berne/Valais (IG Be- BLS Netz AG time for the timetable change of Decem- Wa) was assigned the mandate of project The surveying section of BLS Netz AG was ber 2007, the Lötschberg Base Tunnel surveyor by the contractor BLS AlpTransit responsible for elaborating and updating could be added to the route network. AG. IG BeWa was composed of the fol- the track geometry project and the sys- The Lötschberg base tunnel was con- lowing companies: tem documentation (GIS DfA).

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Breakthrough Lateral- Height Longitudinal Error Effective Tolerance at 99% Level of between [deviation [deviation [deviation [cm] [deviation in tolerance in cm] in cm] in cm] cm] used

Steg – Ferden 8.6 0.5 2.4 Lateral 13.4 25.0 54 % Raron – Lötschen 10.4 1.1 2.3 Height 0.4 12.5 3 % Mitholz – Frutigen 1.5 0.6 0.0 Lötschen – Ferden 2.0 0.3 0.4 Longitudinal 10.3 –– Table 1: Results of the partial breakthroughs. Table 2: Results of the main breakthrough.

Results of the tunnel overall combination measurement me- ably at some places, major global vari- excavations thod (laser scanning). This basis allowed ances occurred. The most important de- us to establish cross sections every 2.5 m viations amounted to up to 24 cm (see Due to the limited monitoring possibilities to permit the comparison of current and Fig. 2). By slightly adapting the track in the tunnel, the surveyor had to live with target profiles. geometry over the whole tunnel length – a certain degree of uncertainty until the With the help of this profile evaluation, without loss of driving dynamics – these end. Only after the final breakthrough the interaction between the different er- deviations, however, could be easily ac- was it possible to verify, with connecting ror components was analyzed. The total commodated. measurements, whether the accuracy re- deviation between the shell construction quirements had been met, with regard to and the project axis consisted of three whether our model assumptions were components: Error of breakthrough correct. Table 1 summarizes the results of compensation after the most important partial excavations. 1. Laying out error of the project survey- On April 28, 2005, the final breakthrough or (PS) blasting (620 392/142 841) was achieved at 2026 2. Laying out error of the company sur- In the tunnel section with drilling and m beneath the Balmhorn between the veyor (CS) blasting excavation, the tunnel floor, in- Bernese Oberland and the Canton of 3. Deviation of the TBM-approach from ner shell, and benches were finished in Valais (Mitholz – Ferden). At the break- the laying out axis of the CS concret at the back already during the ex- through, the control measurements re- cavation. At the moment of the break- vealed the following error of a tunnel ad- The analysis showed that all involved par- through, about 75% of the benches were vance of 20.9 km (see Table 2). ties had met their tolerance requirements. completed and only roughly 4 km were Thus all partial excavations as well as the Because the errors accumulated unfavor- missing. main breakthrough at the Lötschberg Base Tunnel showed very satisfying results. The requirements of the constructor were completely fulfilled.

Error of breakthrough compensation after TBM- excavation In the tunnel sections where tunnel boring machines (TBM) were used the final tunnel floor including kicker (preparation for the inner shell) was installed just behind the TBM. Thus the position of the inner shell and also of the benches was already determined. After the breakthrough and the conclusive calculation of the control point coordinates, the excavated tunnel arch was measured using the Fig 2: Profile measurement analysis Steg – Ferden.

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System concept Measurement Measurement • The motorized total station is fixed on errors (1σ) the track measurement vehicle • 3D-positioning of the track axis by free Position < 0.4 mm stationing over known connection Height < 0.5 mm points Track gauge < 0.3 mm • Automatic measuring of track gauge, longitudinal and transverse inclination Gradient < 0.3 ‰ • Motorized locomotion of the measure- Table 3: average measuring errors ment vehicle with variable increment RACER. • Online-analysis and comparison between required and existing result val- surement results were displayed graphi- ues cally by chart bands showing the differ- Fig. 3: Track gauging trolley RACER. In collaboration with the vehicle’s devel- ences to the nominal value [mm] (Fig 4). opment partners, the measuring system During the period between July 2005 and The front edges of the benches were mea- was developed, the control software was November 2006, after the installation of sured in height and position on the basis programmed, and a prototype of the the slab track, measuring campaigns were of the new control point coordinates (one measuring trolley was constructed. The regularly carried out in sections. In the control point every 25 m). As a result, the operation procedure was optimized with course of several measuring campaigns, track geometry was slightly adjusted in extensive testing and a system calibration over 51 km of tunnel track was controlled. the Mitholz – Ferden section in order to was carried out. These comprehensive In summary, the control measurements place the new track axis exactly between comparative measurements using an in- show excellent results that confirm the the already concreted benches. The error dependent system showed the following high quality installation technology used of breakthrough could thus be compen- average measurement errors (1σ) (Table for the slab tracks on the one hand and sated for and minimal distance inequali- 3). on the other hand the accuracy and reli- ties between banquette position and ref- ability of the RACER. The implementation erence position could be corrected with The contractors’ requirements of innovative solutions and the resulting an axis optimisation. The effective errors The contractor defined the installation tol- saving of time and costs made it possible of breakthrough were therefore compen- erance requirements for the slab track to submit the required results in time and sated for with a minimal adjustment of (Table 4). A distinction is made between with a reasonable effort to the contrac- the track geometry. Depending on the sit- absolute and relative installation toler- tor. uation, this would not be possible with- ance. The absolute tolerance values refer out posterior profiling of the point of to the maximal deviations in both hori- breakthrough. Fortunately, this was not zontal and vertical directions to the pro- Structural monitoring the case in the Lötschberg Base Tunnel, ject axis. The relative tolerances are used A structure this size needs long-term because the error of breakthrough was to evaluate characteristics relevant to dri- monitoring. In October 2003, IG BeWa relatively small and because the general ving dynamics. The measuring interval tendency in the drilling and blasting ex- was fixed at 2.5 m. This resulted in a mea- cavation of the tunnel was to excavate suring section performance of about 150 Survey Parameter Tolerance with an overage. m per hour with the RACER track mea- Position ± 3 mm surement vehicle, which corresponds to an average measuring section of one kilo- Height ± 3 mm 1) Slab track control meter in 6.5 hours. Track alignment error < 2 mm Cant ± 2 mm measurements Results Track gauge –1/+3 mm A new track measurement vehicle (RAC- The results of the final control were com- ER – Rapid Automated Control Equipment piled in the form of differences to the Table 4: installation tolerances 1) On for Rails) was especially developed for the nominal value. The statistical analyses a measuring basis of 20 m the differ- precise control of the track setting (Fig. showed that the installation tolerances in ence between two neighboring track 3). The new surveying concept enables relation to the project axis have been ad- alignments, measured in the middle the contractor to carry out totally inde- hered to at over 99% (Table 5). The few of the string every 5 m must be less pendent slab track control measure- tolerance deviations do not exceed 1 mm. than 2 mm in horizontal and vertical ments. For a clear presentation, all control mea- directions.

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For structural monitoring, heights were stocked at a height control point in the portal sector of the Frutigen connection. The choice of the LN02 height reference system enables on site follow-up measurements without using the orthometric correction system as well as the comparison of measured height differences.

Final consideration From the beginning until the opening of the tunnel, IG BeWa was assigned the surveying tasks at the Lötschberg Base Tun- nel. Worldwide there existed very few projects of such importance and requiring Fig. 4: Differences between the effective geometry of the ballastless track and such accuracy worldwide and therefore the project axis. there was little experience in the laying out of tunnels. The task thus represented asked swisstopo if they were interested in trol the loop short cut over the Lötschberg a big challenge to us. measuring a land levelling line through mountain line as well as the mountain The results of the different breakthroughs the Lötschberg Base Tunnel before it be- tunnel. prove that we have mastered the chal- comes operational, which they accepted. Point groups at every crosscut along the lenge well. The project offered us many The high-precision double levelling car- whole tunnel as well as intermediate exciting moments and we were able to ried out under the supervision of swis- points on the eastern bench side were gain valuable experience. Thanks to the stopo in November/December 2006 pro- fixed with bolts and rivets. In the critical excellent collaboration with all persons in- vided IG BeWa a high accuracy determi- fault zones «Autochthon Nord», «Kar- volved in the project – contractor, project nation of the vertical control points in the bon» and «Jungfraukeil», the density of engineers, geologists, construction man- LHN95 height reference frame. Further- the control net was increased with addi- agers and companies – the Lötschberg more, swisstopo was able to complement tional control points on the western Base Tunnel project will always remain their national height network and to con- bench side. among our best memories.

Absolute installation tolerance Relative installation tolerance Number of Position Height Cant Track Track alignment error measurements gauge Horizontal Vertical

> 3mm > 3mm > 2mm > –1/+3mm > 2mm > 2mm Hans-Ueli Riesen ristag Ingenieure AG 20 440 29 108 11 136 31 Eigerweg 4 100% 0.14% 0.53% 0.05% 0.67% 0.03% 0.01% CH-3322 Urtenen-Schönbühl Table 5: Number of deviations from tolerance. [email protected]

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lifting and alignment system for track po- Railway Infrastructure sitioning. surveying for the Lötschberg Alignment system The alignment system developed by Base Tunnel Rhomberg consists of two components: a lifting wedge, which permits the step- Between 2004 and 2006 the Lötschberg Base Tunnel was equipped for railway oper- less adjustment of the tracks in the sub- ations. The construction costs amounted to CHF 791 million. Wild Ingenieure AG from millimetre range (Fig. 6), and the HERGIE Küssnacht am Rigi were authorized to carry out the surveying contract. The main job track surveying trolley, which displays rel- was to position the 51.6 km long ballastless track in the base tunnel. With the help ative and absolute positions (Fig. 2). of the HERGIE track surveying trolley and the lifting wedge system, developed by Real-time verification was carried out with Rhomberg Bahntechnik AG, the tracks were laid in their specified positions during the total station guided HERGIE track sur- several operations. The high standards of accuracy required for the track laying rep- veying system. The track surveying trolley resented a considerable challenge. The railway infrastructure installation was carried is made of aluminum and weighs only out in a three-shift operation, which required the surveyors to be highly flexible and 25–30 kg. It is fitted with a 100% weath- to closely collaborate with the track construction team. Constant time pressure, shift erproof industrial PC and a touch screen. work, and full on-call availability during the entire construction period put a huge An external keyboard can be added and strain on every single surveyor. it is equipped with a PCMCIA-slot. A LEICA TCA2003 total station was used. The communication between tachymeter and surveying trolley was handled via a For a BT, the ballast is replaced by anoth- radio connection. The position of the B. Tanner er stable material such as concrete. The TCA2003 was determined with the help essential track stability as well as lower of a free station based on track security The railway infrastructure installation was maintenance and operational costs are reference points. carried out by the general contractor advantages in comparison to ballasted The HERGIE track surveying trolley con- «ARGE Bahntechnik Lötschberg» under tracks. The BT provides a service life of 50 sists of the following components: the leadership of two construction com- to 60 years. Disadvantages are significant • Electronic precision inclination sensor panies, Implenia AG and Rhomberg Bah- investment costs and higher airborne for cant (slope or tilt) measurements (ac- ntechnik AG. The consortium included sound emission values. curacy of cant measurements: ±0.4 more than 35 specialized companies cov- At the Lötschberg baseline, a BT was built mm) ering the twelve independent areas of rail- in the base tunnel and in the Engstlige • Distance measurement sensor for the way technology. Wild Ingenieure AG was tunnel (2.4 km in Frutigen); the rest of the track gauge (accuracy of track gauge: assigned the surveying mandate for the tracks (4.6 km) were constructed as bal- ±0.4 mm) railway infrastructure and was primarily lasted tracks. The rigid structure of the BT • Electronic precision inclination sensor active in the areas of road surfaces, cate- requires a higher track-laying accuracy in for rail inclination measurements nary systems, and logistics (construction order to guarantee high-quality driving • Industrial computer with touch-screen infrastructure). Three full-time and up to dynamics (driving comfort and rail wear). (Fig. 3) three additional occasional survey teams The railway infrastructure surveying for • Reflector were employed to carry out the surveying the Lötschberg project started in Febru- work over a period of more than two ary 2003 at the Mitholz test gallery of the HERGIE is based on high-precision, three- years. Lötschberg Base Tunnel. The first BT con- dimensional, real-time single point posi- struction tests were carried out on two tioning. Each measurement point is de- tracks of about 54 m and 36 m in length. termined by seven parameters: its 3-D co- Ballastless track In 2004, two more tests followed in Dorn- ordinates, rail cant, track gauge and the The construction of the ballastless track bin (A) (Fig. 1). Together with Wild Inge- inclination of both tracks. Thus the fol- (BT) was the most complex among the nieure AG, Rhomberg Bahntechnik AG lowing track geometry quality features railway infrastructures. From autumn conducted tests for the BT installation can be defined: 2004 to summer 2006, about 100 work- with a true-to-scale tunnel cross section • the transverse position of the reference ers were on three-shift duty seven days a on a 70 m long track. The task consisted rail (In practice, the reference rail is ad- week in conditions of about 28° Celsius of testing and developing the installation justed, not the rail axis), and high humidity. procedures and the performance of the • the top edge of both rails

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Fig. 1: Test track at Dornbirn (A). Fig. 2: HERGIE track measuring vehicle.

• the rail cant (transverse gradient of the fort and rail wear). The following re- application program. Every 12 m, a point carriageway), quirements were defined for the BT (see was determined left and right on the • the track gauge (distance between the box) bench walls and then continuously inner edges of the rails), The most difficult task was to meet the marked with the help of a snap line (chalk • the railway kilometrage and requirements regarding track alignment line). The main difficulty lay in the pre- • the cant of both tracks (the tracks are error in horizontal and vertical dimen- cise positioning of the track panels by the inclined inwards at a ratio of 1:40). sions (internal geometry). The tolerance track layer. He was required to lay the (= 98.8%-probability) for the adjustment track panels on the adjustable supporting The measured data are stored in the of a support point was ±0.6 mm and re- legs with an accuracy of ±10 mm in po- HERGIE database and can be displayed quired careful and experienced align- sition and ±5 mm in height (Fig. 4). As it graphically or in list format (ASCII format). ment. All other requirements easily could is easier to lift a track than to lower it, the The fixed point coordinates and the route be met with our system. track panels were positioned at 1 cm be- parameters of the track constitute the ba- low the real height. sic data for the rail inspection. These in- Installation of the track During the rough alignment process with clude horizontal and vertical geometric The construction of the BT required five the HERGIE system, the aim was to align data as well as cant data. As the track surveying procedures: the track panels at ±3 mm in position and geometry axis is not identical with the kilo- 1. Surveying for the placement of the 0 mm to –5 mm in height. With the help meterage axis there is the possibility to track sections of a mechanical lift-adjustment device add the kilometrage axis geometric data. 2. Rough alignment of the track panels (Fig. 5), the track is lifted at a distance of In order to improve reliability, the differ- 3. Final alignment of the track panels 3.6 m, moved to the final position and ent components (sensors) can be easily 4. Monitoring during the concrete paving fixed to the adjustable sleeper boots. monitored and calibrated at any time. In 5. Demonstration of the quality of the In order to set the track continously in the addition, the orientation of the total sta- track geometry required position, iterative alignment pro- tion can always be controlled and adjust- cedures were necessary. Depending on ed from the track surveying trolley. The installation of the BT was carried out HERGIE is powered using a 12 Volt car in 2160 m cycles. For logistical reasons, battery (45 Ah), which ensures the con- 18 m long preassembled track panels, in- tinuous operation of the system for twelve cluding the track sleepers, were trans- hours. ported to the base tunnel and assembled together. Installation tolerances In order to install them with as much pre- Due to the rigid construction of the BT, cision as possible, the extended carriage- the installation tolerances are much way and the axis distances at the bench- higher than for ballasted tracks. This is the es were marked beforehand. The stake- only way to guarantee high-quality dri- out was essentially surveyed with a total Fig. 3: Touch Screen with measuring ving dynamics (for example, driving com- station on the basis of a track stakeout data display.

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In the next step, the track panels were Installation tolerances in horizontal ±3 mm fixed every 1.8 m with concrete supports and vertical directions (external geometry; and the now unnecessary sleeper boots measurement basis: adjusted control were folded upwards. The track sup- network) porting slab, about 25 cm high, was then set in concrete, thus fixing the concrete Track alignment error <2 mm supports. (internal geometry: horizontal and vertical, The sleepers were still exposed, but from measurement basis 20 m, difference between that moment on the tracks could only be two neighbouring track alignments <2 mm, moved only over a small area with the help measured every 5 m in the middle of the chord) of lifting wedges, it was very important to perform the preceding rough align- Installation tolerances cant ±2 mm ment with sufficient accuracy. Even small deviations made the final adjustment with Deformation ≤0.5‰ the lifting and alignment system difficult or even impossible and time-consuming Installation tolerances track gauge –1/+3 mm emergency solutions had to be found. (standard deviation ≤1 mm) The final adjustment of the tracks (Fig.. 6) was carried out with the HERGIE track sur- Installation tolerances rail inclination min. 1:45, max. 1:35 veying trolley and the lifting wedge system as well, this being the last adjustment Installation tolerances longitudinal ±10 mm procedure before concreting the track support point distance angle accuracy: ±10 mm sleepers. The final adjustment required maximum accuracy, the tracks having to be adjusted at ±0.2 mm in position and the precision of the track positioning and panels was positioned more to the left or height. Experience has shown that the air the accuracy of the rough alignment, one the right of the intended final position. flows and turbulence inside the tunnel to three alignment procedures were nec- This was therefore taken into account were problematic. To counteract this, on- essary. One difficulty lay in the fact that, when adjusting the position. ly two track panels (36 m) per total sta- as a result of overcorrecting, the position In addition, the rail inclination was con- tion setup were positioned. of the global track could shift again in the trolled during the first alignment proce- The track was adjusted every 1.8 m with completed and already corrected posi- dure. The rails had to be curved inward the help of a pair of lifting wedges fixed tions. This procedure required a high de- at a ratio of 1:40. With the help of 0.1 under both rails. One wedge served to ad- gree of skill: on the basis of the required mm to 0.5 mm thick fastening clips, the just the position and height of the right muscle strength to move the track, it had required rail inclination could be adjusted rail and the other the position and height to be determined if the preceding track at the track holder. of the left rail. This procedure required

Fig. 4: Installation of the 18 m long track panel. Fig. 5: Rough track positioning.

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Fig. 6: Fine adjustment of the track panel with the me- Fig. 7: PLASMA longitudinal chord-based track. chanical lift-adjustment device. great precision and several iterative align- 51.6 km long BT was installed without re- stall 7.3 km of track supporting slab on ment procedures. Overall, the BT rails quiring rectifications and could be hand- the Berne side beforehand, which con- were adjusted with the help of more than ed over to the constructor for test drives siderably reduced the subsequent con- 57 300 lifting wedges and by muscle pow- in June 2006. struction time for the BT (Fig. 8). The as- er. Of decisive importance for this perfect signment was to provide surveying ser- Half a work shift (about 4 hours) later, the achievement were, above all, the excel- vices for the total-station controlled adjusted tracks, with the track sleepers, lent collaboration and the great mutual slipform paver. The installation of the were set in concrete. During the placing helpfulness of all people involved. To- track supporting slab was performed dur- of the cast concrete, monitoring was car- gether with specialist knowledge, regular ing normal daily shift operations and was ried out by a longitudinal chord-based maintenance, adjustments, calibration of supervised by a surveyor. He was assigned track. The Rhomberg PLASMA longitudi- the instruments, and the track surveying the task to reposition and realign the to- nal chord-based track (Fig. 7) was direct- trolleys lead to success. The HERGIE track tal station for the paver control system ly connected to the concrete paver unit, surveying trolley was perfectly suited to every 50 m and to monitor the automat- pulled behind. It surveyed the relative the task because it was reliable, solid, and ic control of the paver by periodic sam- height and position change, cant mea- of light construction. The precise and pling. Moreover, in a one-man operation, surement, track gauge, and distortion. dense base network in the tunnel was an- he had to monitor the cured track sup- The measurements served to maintain other basic prerequisite for the good reporting slab. quality assurance of the track geometry sults. during the concreting. If the PLASMA Despite the seemingly monotonous and track had measured deviations in the ad- repetitive adjustment measurements the Track holder justed track geometry an audible alarm task was anything than boring for the sur- Over 10 000 points had to be staked out signal and rotating beacons would have veying team. In fact, the surveyors were at ±10 mm and ±3 mm for the 60 km been activated. faced with and challenged by new and long catenary system. Most points were After the concrete had cured the 18 m unexpected problems on a daily basis. The staked out in catenary support structure long track sections were detached from intense time pressure was not just a bur- shell. The staking out was performed with the concreted sleepers and removed. den, but could be motivating as well. a total station and a track stakeout ap- Long-welded rails (running rails) 120 m plication program, taking into account long were then placed in the sleepers. The the track cant. The staked out points were final control of the running rails was car- Track supporting slab secured with a borehole and color mark ried out on these long-welded rails with Once a few kilometres of BT had been in- that defined one of the nine different the HERGIE track surveying trolley. The re- stalled on the Wallis side, the shell work drilling patterns for the anchor drillings. sults were displayed graphically by a dia- on the Berne side could be completed dur- The staking out of the about 100 tension gram and with a list containing statistical ing the second half of 2005. For the first wheels for the re-tensioning system of the key figures. The measuring drives with the time, the tunnel infrastructure could be catenary wire was particularly time-con- SBB diagnostics vehicle confirmed the ex- installed from both sides of the tunnel. To suming with 14 points each. In the drilling cellent quality of the track geometry. The speed up the work, it was decided to in- and blasting sections, a formwork curved

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for the installation of the BT. Along with the tunnel shell, the railway technology surveying team took over the track displacement monitoring network and thus its maintenance. The client’s surveyor performed the elaboration of the basic control network. A few track reference points had to be replaced and newly determined. One of the last tasks was to update the project point collection for the Federal Railway's central data base (DfA) and its structured data supply.

Success, challenges and thanks

Fig. 8: Installation of the track-supporting slab with the formwork finisher. The surveying of the railway infrastructure was in all respects an interesting assign- over two radii was staked out beforehand things an important street and rail bound ment for Wild Ingenieure AG. Thanks to on the irregular shotcrete surface. This transfer point, two large halls each, a con- a good organization, and motivated and was done with the help of metres-long, crete batching plant, a residential mobile flexible surveyors, we were able to carry tear-resistant plot templates that were fit home camp and several office trailers. The out all tasks reliably, quickly and without over three staked-out points and on temporary railway tracks consisted of incidents. Our fundamental knowledge which the curved surface line was traced. roughly 9 km of track and 37 track switch- on railway construction contributed to The staking out of the catenary points was es. The staking out of those temporary in- this success. performed during the few days of prepa- stallation sites was also part of the sur- For the major and time-restricted surveys, ration preceding the next BT installation veying assignment. the surveyors had at their disposal a com- cycle. plete roster of measuring equipment, ranging from spanners to track surveying Additional surveying trolleys and total stations, in double and Ballasted track multiple versions. All reserve material was The 4.6 km long open aboveground sec- services transported along in a material container tions of the Lötschberg baseline were Aside from the main surveying work for on rails and was therefore always at hand equipped with a ballasted track that in- the track, the catenary system and the lo- and available. To recharge the various bat- cluded a 160 m long high-speed switch. gistics, many additional surveying tasks teries, a power supply was available every The conventional rail construction re- were performed for other specialist areas. 333 m in the cross-galleries. Continuous quired relatively few stakeouts. The main They were often limited to special calcu- processes permitted clear transfers at shift task was therefore the transfer and man- lations on the basis of track geometry da- changes, even in hectic circumstances. A agement of the numerous different track ta or to simple stakeouts or recordings. real puzzle was the installation of the two geometries and temporary track refer- One of the tasks consisted of establishing 160 m long high-speed switches in the ence points in each construction phase. requirement profiles for laser scanning BT. This was hardly astonishing as the con- The collected data served as a basis for pictures and their acquisition. The tunnel struction tolerances for the concrete providing installation lists and tamping tube tolerances data provided by the con- sleepers were higher than the predeter- machine files for the tracklayers. structor were insufficient for an optimized mined installation tolerances for the installation of the BT. The exact position switch. After numerous adjustment pro- of the tunnel floor, the shells, and espe- cedures of the main track and the safety Logistics cially the drainage shafts located inside track, the switch was adjusted in parallel Logistics played a central role in this large- the track were of major importance for a using two track-surveying trolleys. A few scale project. Five-hectare surface instal- smooth course of construction. It soon be- hours later, the switch was positioned in- lation sites for the railway infrastructure came clear that precise and complete side the required installation tolerances were set up in Raron and Frutigen. Among recording of the base tunnel’s overall and could be concreted. With great ex- other things, they included among other structural work could save a lot of time perience and confidence, the adjustment

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of the second switch was undertaken half order to maintain the optimal operating ration for the next work cycle, the re- a year later. Although the knowledge and cycle. maining survey works, analyses and pro- tricks gained from the first installation A normal shift for a surveyor usually be- tocols had to be completed. caused fewer headaches, the adjustment gan 1–2 hours before the actual start of Over the term of two years, this project of the second switch didn’t take less time. the shift. From the surface installations required extraordinary efforts from our After about 48 hours, the second high- site, he contacted the surveyor inside the surveyors. This was only made possible speed switch was also installed within the tunnel by radio and enquired about the through their exceptional personal com- required tolerances. One of the greatest progress of work and possible problems. mitment and compromises in their private challenges for the surveying team, how- He then boarded the staff train for a 1–2 world. I would like to express once more ever, was to work in three-shift operations hours journey to the front of the installa- my sincere gratitude to our surveying under difficult climatic conditions. The tion site. When taking over the work, he team and their families. surveyors were furthermore required to first checked at which niche the replace- be available and competent for emer- ment batteries where charged and then gencies around the clock during the shift performed a complete calibration of the cycle assigned to them. sensors. After eight hours of work in the The surveying work was strictly bound by tunnel, the staff train took him back to the operational processes and work the surface installation site. A long and progress of the tracklayer team. It is well tiring 10–12 hour working day ended known that surveyors usually have to ad- with a warm meal and a beer in the can- Bruno Tanner just at very short notice to the timetables teen. Pat. Ingenieur-Geometer of others. It was no different during the During the installation of the BT, our sur- Wild Ingenieure AG construction of the BT. Shifts were regu- veyors were exclusively assigned to three- CH-6403 Küssnacht am Rigi larly cancelled or had to be doubled in shift operations. In the 3–5 days of prepa- [email protected]

95 AlpTransit Gotthard

Deformation Monitoring – Challenge Accepted

Building activities, like the NEAT, always include a large number of challenges. The participating companies need and are willing to face these challenges. Of course, this is also true for deformation monitoring, aboveground and underground. This short article deals with some of these challenges, with a hint of humor.

been selected, but how to establish a re- M. Bertges liable communication link? Of course, mountaineering is great fun during holi- Today, deformation monitoring is part of day but during normal working time, it’s daily work for most surveyors. Being just too expensive. Unfortunately, for asked about the dedicated tasks for mon- more than half a year, the only real op- itoring, they will use terms like «measur- tion for accessing the GNSS stations is a ing», «analyzing», and «visualizing». This helicopter. And to add insult to injury, the is correct for the standard, manual mon- weather conditions are harsh, with only itoring. But for automated deformation GSM, no GPRS/UMTS access, and no Fig. 1: GNSS-Station. monitoring, one very important term is spare frequencies for point-to-point radio missing: «data transmission». links. To complete this challenge success- el operations being correct. A solar pan- The necessary skills for this task normally fully, a network of autonomous sensor el needs sun to produce power. If the pan- exceeds what a geomatics engineer had systems was necessary. el is mostly snow-covered, the remaining been taught. This is not a serious deficit ARGE Los349 had chosen to use the DC3 power is not enough to drive a GNSS de- in teaching geomatics. The skills are the deformation control system. The DC3 us- formation monitoring station … quot er- ones of a communication specialist, like es small microcontrollers, which perma- at demonstrandum. The loss of contact an electrical engineer. This demonstrates nently monitor not only the GNSS sensors with another station during the summer perfectly the interdisciplinary cooperation but also the GSM modules. In case of any was caused by some «smart guys», who in engineering today. malfunction or abnormal operation, the had the idea those solar panels, the charg- microcontroller resets and reinitializes the er and the batteries (about 60 kg weight!) sensor and GSM module. There is an in- could be used perfectly in a new envi- GBT – ARGE Los349 tegrated scheduler that can be used for ronment, like a cozy mountain hut or In summer 2002, we were asked to pro- offline measurements. A user ID and pass- something similar. Unfortunately, they de- vide an automatic deformation monitor- word control access to the system. cided to prove their theory. ing system. The challenge was «just» the Everything was working fine, but all par- By summer 2007 five additional DC3 communication between the sensors – ticipants had to experience the special GNSS monitoring stations had been in- the measurement modules –and the main characteristics of GSM cells first. During stalled. A network of ten GNSS stations computer – the «analyzing module». So the skiing season, occasionally some of now monitors the movements above the what was the problem? During construc- the stations were not accessible due to a base tunnel. tion of the tunnel and the Sedrun multi- GSM cell overload. The low signal power function station, ARGE Los349 had been of the GSM signals in this high mountain Faido MFS–Amberg assigned to monitor the movement of se- area could be handled by using directional lected points in the terrain. It was decid- antennas. For a proper pointing to the cell Technologies ed to use GNSS, but the points were at base station, the integrated test opera- In spring 2006, several rock bursts oc- an altitude of between 2000 m and 2700 tions of the system could be used. Dur- curred during construction of the Faido m in a high mountainous area. Solar was ing the first winter, the DC3 server lost MFS. The general public experienced the the first choice for a power supply and contact with one station. A checkup by rock bursts as seismic events. Responsible the suitable GNSS receivers had already helicopter proved the theory of solar pan- for the rock bursts were fault zones in the

96 AlpTransit Gotthard

mountains near the Faido MFS. To assist The resulting blockage of the highway acknowledgement was received in a de- the geological research of the fault zones, would cause severe traffic jams. Any com- fined timespan, a second alert was sent two autonomous working monitoring plex system, especially with human inter- by a voice call and a prerecorded voice systems had to be installed in the Faido action, has many sources of false alarms. message. SMS text and voice messages MFS. Two identical DC3 systems with a Bearing in mind the universal validity of depended on this kind of alert. If no ac- total station, a software module for con- «Murphy's Law», the worst-case scenario knowledgement was received from the vergence analysis but without active alert- would happen during holiday season and person, the alert was handed over to the ing were installed. a weekend. No doubt this was something next person in the group. The challenge was the power supply. Hav- that no one was willing to imagine. So Of course, some of these smaller «chal- ing no permanent access to the 230V the challenge was to deliver a system with lenges», all participants can hopefully power lines, the only possibility was to use extremely high reliability and complex but smile about today. Like the broken cable, a connector in one of the many power robust mechanisms for alerting. which had to be repaired temporarily be- distributions on the construction site. So The first step was to distribute the differ- cause of time pressure and was drowned the two DC3 systems had to share their ent sensors – geotechnical sensors, total with the next rain on the next day, deep needs of 230 V-power with the needs of station and GNSS – to several separated inside a borehole. Or the spiders that the tunnellers. A UPS served as a buffer deformation-monitoring systems. The found the rain protection of a prism to be for about 1.5 hours of operation. The communication inside each monitoring very suitable for their new home. The in- available means of alarm of the DC3 sys- system and the interconnection of all the frared beam of the total station could not tem were intended to warn the tunnellers systems were IP based. The main servers penetrate the spider’s nest. And don’t for- to plus in the DC3 power connectors af- and communication modules in an air- get the ants around the electronic boxes ter removing their tools from the power conditioned 19’’cabinet had been placed in one borehole, and that piece of distribution. During installation, a large in a container near the construction site. hosepipe, which suddenly appeared to be number of power sockets were available. The second step was to divide the geot- a snake. Not to mention the radio link, So nobody expected any problems for the echnical sensors into two groups, each which worked perfectly for a long time … future. handled by an autonomously running until someone else on the site started us- The following 1–1.5 years proved this idea DC3 system. Both systems were using UPS ing the same frequency … occasionally. to be wrong. We found out that the num- to be able to work for about 90 minutes Last but not least, it is a pleasure to thank ber of available power sockets was not with no main power supply. In case there all the colleagues of the participating enough. Two flashing lights were added was a complete breakdown of the cable companies for the cooperation during the to the illumination of the Faido MFS and connection between the two geotechni- past years. Only in cooperation like this, during their 1.5 hour of operation, they cal-monitoring systems and the contain- is it possible for us to accept all these chal- alerted nobody to anything, especially not er site, backup Wi-Fi links had been in- lenges and to make our contribution to to reinsert the power connectors of the stalled. the construction of the Gotthard Base monitoring systems. Luckily, during each As a last step, special software was de- Tunnel. of their shifts, the surveyors made their veloped that allowed the analysis of the way along the two systems, thus they sensor values with regard to the causal in- were able to minimize the loss of data. terconnections between sensors in one borehole, sensor groups, and neighboring boreholes. The result of this analysis CBT – IG Ceneri Los704 had been the alert levels «hardware The northern tunnel portal crosses below alert», «warning – yellow alert», and «red Martin Bertges the A2 highway, which leads to the Ceneri alert». Dr. Bertges Vermessungstechnik pass. This is the only north-to-south high- A multilevel concept was necessary to ful- Flurstrasse 7 way through this part of the Alps. The fil the needs for alerting different user DE-66887 Neunkirchen am Potzberg worst-case scenario would be a defor- groups. The first alert was sent by SMS to [email protected] mation or a soil flow during construction. the first person in the user group. If no www.deformationsmesstechnik.de

97 AlpTransit Gotthard

300 surveyors acknowledge Overview of the diverse surveying tasks many years of precise work In the afternoon, a series of brief presentations by surveying specialists who were Masterly surveying performances in the world's longest railway tunnel: only eight cen- involved provided an impressive overview timetres horizontally and one centimetre vertically – those were the deviations at the of the numerous tasks of the geomatics final breakthrough of the Gotthard Base Tunnel on October 15, 2010. At a specialist discipline. The spectrum ranges from con- conference held at the Swiss Federal Institute of Technology (ETH) in Zurich, some 300 trol of the drives through monitoring of surveying experts from Switzerland, Germany and Austria paid tribute to the preci- dams and motorways to laser scanning of sion that was achieved. the tunnel vault. It also includes monitoring the laying of the permanent railway track in the tunnel, which must be accurate to as little as one tenth of a millime- tute of Geodetic Metrology and Engineer - tre. R. Probst, D. Fasler Isch ing Geodesy, Professor Dr. H. Ingensand). The challenges presented to surveying by Specialist event marks tunnel construction, and the Gotthard Cordial thanks to final breakthrough of the Base Tunnel in particular, were examined from a theoretical and practical perspec- participants and sponsors Gotthard Base Tunnel tive. Hilmar Ingensand, Professor of Engi- Significant contributors to the success of At the specialist conference, «With mil- neering Geodesy, described the various the event were: The organisation team of limetre accuracy through the Gotthard» new and further developments in the field Professor Ingensand's Institute of Geo- held at the Hönggerberg Science City of of metrology and precision instruments detic Metrology and Engineering Geo- the ETH Zurich, the many different chal- that were stimulated and accelerated by desy at the ETH, led by Susanna Naldi; the lenges of underground surveying were the AlpTransit project. From the viewpoint Head of the Construction Hall, Dominik discussed. The event took place on Octo- of the Gotthard Base Tunnel Surveying Werne, and his team; Daniel Bäni, who ber 29, 2010, exactly two weeks after the Consortium (VI-GBT), which was tasked coordinated setting up the exhibition; SV successful final breakthrough in the Got- with responsibility for surveying in the Service, who provided the excellent meals thard Base Tunnel between Sedrun and Gotthard Base Tunnel by the tunnel own- throughout the day and evening; the au- Faido. Around 300 surveying specialists er, AlpTransit Gotthard Ltd, Roland Sten- dio-visual team, who were responsible for and geomaticians from Switzerland, Ger- gele described the discrepancies between the video and audio systems, as well as many, and Austria were in attendance. theory and practice that were encoun- the Media Office and Geomatics Depart- The event was organised by AlpTransit tered during work on the tunnel in the ment of AlpTransit Gotthard Ltd. Without Gotthard Ltd. and the ETH Zurich (Insti- last 15 years. the generous contributions of the spon-

Fig. 1: The specialist audience attentively follows the pre- Fig. 2: Participants at the conference obtain information sentation by Professor Dr. U. Weidmann. about the latest developments in metrology.

98 AlpTransit Gotthard

Fig. 3: Former and current employees of the Gotthard Base Tunnel Surveying Consortium (VI-GBT) and AlpTransit Gotthard Ltd. sors, the event could not have taken place. Bronze Sponsors, Dr. Bertges Surveying Rahel Probst We wish to thank the Gold Sponsors, BSF Systems, Goecke, Grunder Engineers, In- Daniela Fasler Isch Swissphoto, Grünenfelder and Partner, genieur-Geometer Schweiz, and Ristag AlpTransit Gotthard Ltd. the TAT Consortium, and the Federal Of- Engineers. Special thanks also go to the Zentralstrasse 5 fice of Topography; the Silver Sponsors, Gerold and Niklaus Schnitter Fund for the 6003 Lucerne, Switzerland Amberg Technologies, Gisi e Bernasconi / History of Engineering, ETH Zurich, for its [email protected] Geofoto and Studio Meier; and the supporting contribution. [email protected]

Exhibitors at the specialist conference

In addition to networking and culinary aspects, the event ner, Federal Office of Topography, Department of Civil, «With millimetre accuracy through the Gotthard» also Environmental and Geomatic Engineering ETH, DMT, Dr. provided the opportunity to obtain information about in- Bertges Surveying Systems, Society for the History of Geo - novations in the geomatics field at the numerous stands desy in Switzerland, Goecke, Leica Geosystems, Ristag of the following exhibitors: Engineers, Schenkel Surveying, Technical University Mu- Amberg Technologies, Fahrbahn TTG Consortium, Grun- nich (Chair of Geodesy) and VMT. der Engineers, BSF Swissphoto, Grünenfelder and Part-

99 100 We guarantee 750 billion Swiss francs of mortgage loans for our economy Trading in land and property is an important part of the Swiss economy. Land can however only be traded if the property rights are clearly defined and documented. We, the Engineering Surveyors, master this challenge with the official cadastral survey. We therefore contribute to guarantee 750 billion Swiss francs of mortgage loans for the Swiss economy. As engineering surveyors, we intervene more than any other professional group at the interface between public and private action. Since more than 100 years, we help to ensure property by means of a clearly defined distribution of labour according to the well proven principle of Public Private Partnership. Only people who have passed the federal patent exami - nation are allowed the title of «engineering surveyor». We set the highest standards for the professional competence and the personal aptitude required for our special tasks in the service of the official cadastral survey.

We are organized into an association of Swiss Engineering Surveyors (IGS) The Swiss Engineering Surveyors (IGS) is the Swiss employers’ organization of Engineering Surveyors. Our commitment is primarily focused on developing our profession – in geomatic engineering, land management and corporate management. As employer’s organisation, IGS represents the interests of the profession externally, for instance vis-à-vis public authorities, the political world, the public, the economy and partner organizations in Switzerland and abroad. We are committed to a healthy economic competition among our members. IGS promotes entrepreneurial thinking Retaining our own autonomy, we act for an education and acting in compliance with the ethical principles of our at the highest standards and a professional practice of profession. As employer’s organization, we are working to equivalent quality. We also represent our interests on create a favourable framework for entrepreneurial freedom an inter national level, for example in the International encouraging independent thought and action, as well as for Federation of Surveyors (FIG). the personal and professional development and performances The association represents around 230 surveyor’s of our employees. Although Switzerland is not a member of offices with roughly 370 Engineering Surveyors and 3300 the EU we are actively involved in European associations. employees throughout Switzerland. We provide private developers with comprehensive land information We quickly and reliably supply any required updated land information and in doing so support the realization of constructional concepts.

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Model projects: • Hydraulic engineering, flood protection, renaturation • Land management for agricultural soils and constructible land • Collection, management and updating of land-related data Contact • Creation and management of municipal and regional GIS- Ingenieur-Geometer Schweiz (IGS) centres Kapellenstrasse 14 | Postfach 5236 • Operation of Cadastre of public-private ownership restrictions 3001 Bern, Switzerland • Implementation and updating of the official cadastral survey Phone +41 (0)31 390 98 84 according to the standards AV93 and DM01 Fax +41 (0)31 390 99 03 • Engineering surveys [email protected] | www.igs-ch.ch