4 Tunnel Surveying : Tunnel technology for the future

The Alp Transit Gotthard is an ambitious railway construction project, which will incorporate the world's longest railway tunnel of 57 km travelling through the Swiss and under the St. Gotthard massif. Future passenger trains will journey at speeds of up to 250 km/h, adding further to the highly successful European high-speed network and bringing a huge reduction in travelling time. The combined surveying systems of Leica Geosystems and Amberg Measuring Technique Ltd are greatly assisting the tunnel workers in their day- to-day work - not only reducing time needed to ensure that excavation is correctly undertaken, but also mak- ing the whole construction process much more efficient and accurate. In order to integrate connecting galleries every on collisions is eliminated into the 325m. The entire tunnel and the two pairs of cross- modern rail network, lines construction has been over tunnels allow the The Gotthard Base Tunnel has must be prepared which divided into five sections, trains to move from one been divided into five sections: can be travelled at high each with its own separate tunnel to the other, which is Erstfeld, Amsteg, Sedrun, speed. The Gotthard Base access point: particularly important dur- and Bodio Tunnel, which will cost · Erstfeld - northern portal ing maintenance work. The around seven billion francs, · Amsteg - horizontal access Sedrun and Faido sections is thus the foundation stone tunnel, 1.2km long each include a Multi-func- of the Swiss railway of the · Sedrun - two blind shafts, tional Station that, in the future. The connections in 800m deep and 8 m in event of an accident, pro- international transport, diameter accessed vides safe rooms for pas- built up around the nodes through a horizontal sengers and emergency of Zurich and Milan, will tunnel about 1km long train stations. Connecting become considerably faster, · Faido - a 2.7km long galleries provide track thus presenting a real alter- inclined access tunnel cross-over tunnels, a venti- native to travelling by car (adit) with a 12% gradient lation system and a quick or by air. It is anticipated and a height difference of route to the outside in the that between 200-220 300m event of an evacuation. goods trains will run daily · Bodio - southern portal These intermediate access following its completion. headings not only allow The Gotthard Base Tunnel these safety features to be The Gotthard Base Tunnel will pave the way in quality incorporated, but also allow consists of two single-track and safety with an extreme- up to four Tunnel Boring tunnels that lie approxi- ly comprehensive safety Machines (TBMs) to operate mately 40m apart and these system. By using two tun- at the same time thus are linked by a series of nels the possibility of head reducing the overall con- Tunnel Surveying 5 struction time of the tunnel Previously, in order to Setout made easy by almost half to nine position the arches accurate- years. ly in a tunnel, the excavation Obviously in the construc- crew would finish a tunnel tion industry, time is The geology and rock type to the approximate profile money and as such the of the area determines the required within which to fit Gotthard Base Tunnel is a method of tunnelling and the arches. The site survey- 24-hours a day operation therefore engineers must ors would then be called with eight-hour shifts for create different tunnelling back on site to examine the each six-person tunnelling profiles according to the work, place the arches in the crew. Every four days there rock encountered. Nearly 90% of the Gotthard Base face and then direct further is also an eight-hour period Tunnel has rock that is suit- work. If the face had not when the machines under- able for mining using TMBs, been excavated to a large go maintenance. Handover Leica TCR1105 total stations are with the remaining areas - enough profile, then the between shifts only takes a mounted high on the walls the Sedrun section and the arches had to be removed couple of minutes and one where they undertake surveying multi-function station at and the excavation contin- or two people per crew are and monitoring work Faido - having to be exca- ued. Alternatively, if the pro- trained in using the TMS vated by drill and blast. file was too large, the quan- and are responsible for Over major sections of the tity of shotcrete required in passing on information to tunnel, the overburden will between the arches would the next shift. The Leica be extremely high, includ- be increased considerably. TMS greatly assists in a ing 5km with more than Both activities significantly smooth handover and the 2000m where rock tempera- increase the costs of the continuation of work tures can be as high as 45oC. These conditions all tunnel construction. because all the project data affect the methods and is already there on the complexity of the tunnelling In the tunnels, Leica machine. operation. TCRA1105 total stations are mounted high on the walls "The principle is very Tunnel Measurement and are controlled by the simple: the installation is System Leica TMS which automati- undertaken by the surveyor cally performs the surveying and then we can explain It is in the depths of the and monitoring work such and train people so they tunnel at Faido that Leica as alignment, excavated know what points need to Geosystems and Amberg profile, position of arches, or be entered into the Measuring Technique Ltd thickness of shotcrete program," Kurt said. "We are providing an integrated required. Each Leica total prepare the information surveying solution for the station contains the power- plate describing what the drill and blast method. Over ful onboard LEICA TMS section is and what the 300m of this section has SETout PLUS software. The points are. These people been excavated so far, and surveyor prepares and can then use the instru- due to the immense pres- enters all the project data ment alone without any Senior Surveyor from Amburg sure from the rock, the tun- and geometry using the more support from the Measuring Techniques, Kurt nel in this section is being Leica TMS OFFICE on an surveyor." Weidner excavated in two sections - office based computer and firstly the upper part of the then transfers this informa- Once installed, the opera- face and then the lower tion to the total station via a tion of the system is car- part, known as the heading PCMCIA card prior to job ried out by the construction and the bench. Approx- commencement. site personnel, who do not imately 450kg of explosive need to have any specific is required to advance each Kurt Weidner, Senior knowledge about sur- round and the tunnel Surveyor from Amberg veying. The key benefit of advances at around one to Measuring Techniques, is this approach is that there three metres per day. one of the contracting is no delay waiting for the surveyors on-site at Faido. surveyor and the work car- The LEICA TMS (Tunnel "We are using completely ried out by the excavation Measurement System) Leica tools here at this site," crew is more accurate and offers automatic profile he said. "TMS, the combi- productive, thereby surveying and setting out nation of the Leica total improving the process and using total stations from the stations and the Amberg saving costs. LEICA TPS 1100 Profession- software, is currently being al series. The concept used in four tunnel sections. "During any one shift there behind this was to identify The total stations are used are six surveyors available the production tasks directly for the controlling of on-site. The new system required for the job and to the arc position and the saves a lot of time and the automate them so that a profile situation after we drill surveyors are freed-up Surveyor Elke Fischer prepares non-surveyor, such as the and blast and to ensure that to continue with design and enters all the project data tunnel foreman, could carry the surface of our gauge is work and solving other and geometry using the Leica out the setting out. in the right form." problems." TMS OFFICE 6 Tunnel Surveying Adverse conditions at "Before we were never able About Amberg Faido to have this control and had The highly specialised companies of the Amberg to use a tape." Group cover a wide spectrum of underground Although geological sam- construction tasks, developing solutions in order pling and assessment can "Electronic Distance to advance into new dimensions of underground be carried out prior to the Measurements (EDM) commencement of tun- defined on the integrated construction. Amberg Engineering Ltd. plans and nelling, it is not until the software of the total station designs new structures and refurbishment excavators actually begin allows us to have each projects, provides site management, delivers work that they know for point measured precisely expert opinions and carries out damage and certain what type of rock is after 10 seconds," Kurt said. state assessments. Amberg Measuring Techni- to be encountered. This has "Alternatively we can use a que Ltd. develops systems and instruments that been the case at Faido special function of the pro- address measurement problems in underground where, in April of 2002, a gram when we want exact construction and the rail industry, which includes partial collapse occurred in control so that we can also initial reconnaissance, site supervision and the cross cavern vault, leav- select individual points. ing a cavity about eight This is the part that is new surveying. metres high. Despite the in surveying." prediction of exploratory drill cores, a fault zone con- Monitoring The tunnelling foreman can taining a very poor rock do routine production layer of silty Lucomagno As the tunnel progresses, it surveying tasks using the geniss was encountered. is necessary to monitor the TMS SETout PLUS in This meant implementation tunnel profile for deforma- production mode, including: of modified work methods tion. A lot of pressure is · Drill and blast and strengthening of the built up using the drill and · Conventional advance excavation support was blast method, and as such · Roadheader advance necessary with deformable there is normally a differ- · Jetting and pipe umbrella steel arches and a dense ence between the power- · Alignment laser anchoring system. point direction and the con- · Position arches trol point at the front. A "Deformations required Leica TCA2003 is used for "It's very easy to use, some re-design of the tun- this type of monitoring as it people are working with it nelling," Kurt said. "We is more precise when mil- and they are happy with its prepare the theoretical pro- limetre accuracy is needed. performance. The remote file based on the design Yellow targets with a white control can be held in your drawings and change the faces are used for reflec- hand, directly in front of profile according to the rock tion, and these are placed you or you can control it conditions. With the LEICA in the heading (at three over a wireless system," TMS, to prepare only a few points) and the bench (two Kurt said. "We also have a coordinates of the profile, is points) of the tunnel. special place for the no longer a problem. computer that is set back Previously, this all had to be "Over 300-400 targets have 100-150 metres away from done manually and took a been installed so far for the work, for safety lot of time." deformation monitoring," distance." Kurt said. "These points are The Sedrun section and the Profile measurement controlled one to two times multi-function station at Faido - a week in order to provide a have to be excavated by drill Another program available record of the movement. and blast as part of the LEICA TMS is The highest deformation the LEICA TMS PROFILE measured so far has been which enables profile meas- 50 cm. Using the software urement and monitoring, you can see the calculation providing a comprehensive and check the points from comparison of design vs 50-100 metres being the actual measurement and current head. Over a four- project data. month period, the control points are checked twice, "We can also now monitor and the control brackets are our precise position in the checked once every four tunnel. We can establish if months. we are in exactly the right Bt position for the profile, by comparing the measured tunnel meter with the theo- retical one and we can adjust this immediately if it is wrong," Kurt said.