Tunnelling Market in Finland

Tunnel 3/2011 ITA/WTC 2011 in Helsinki 19

The following article from the organizing Fin- transport more than 100,000 tation planning with design of nish Tunnelling Association welcomes the parti- passengers per day [2]. the rock structures as one of the The automated metro traf- central tasks. A large amount of cipants at the ITA-AITES World Tunnel Congress fic will go in 2 parallel, 13.9 km geological data was needed to 2011 in Helsinki. It gives an overview over the long rock tunnels (Fig.1). As total, ensure the detailed plans for the most interesting tunnelling projects in Finland. 8 stations will be built in rock. 15 rock structures. The main part of vertical shafts with emergency the surveys was therefore main- exits are designed to serve tech- ly concentrated on rock quality Prof. Pekka Särkkä, Chairman Scientific Committee WTC2011, nical needs as well. The 2 metro investigations. The rock enginee- Helsinki/Finland, www.wtc11.org tunnels will be connected at ring design was mainly focused intervals of 100 to 150 m with on project realisation both in The history of rock engineering destrian precincts, parking and crosscuts for pressure equalisa- terms of time planning as well dates back some 6,000 years. It other facilities to city centres. tion, emergency connections, as of cost planning. has since progressed in a num- Environmental problems and maintenance work. Nine ber of waves, the first of which coupled with a growing aware- access tunnels will be made for 1.3 Rock mechanics design was prehistoric Man’s search ness of them have provided the construction and maintenance. All stations and track switching for shelter from the elements impetus for the fourth wave. The The stations will be approx. 200 halls were set to be modelled and refuge from wild animals minimisation of environment im- m long rock halls with a span of with 3-D rock mechanical ana- in underground caves and ca- pacts, nature conservation, the 23 to 25 m. The project requires lysis tools to simulate the beha- verns. Mines, fortresses, fortified desire to protect old urban envi- the removal of around 1.6 million viour of the rock material and palaces, temples and churches ronments from redevelopment, solid m3 of rock. The tunnels and to quantify the final amount of were all built into the bedrock and stricter legislation have all stations will be excavated with reinforcement needed. All tunnel - some as monoliths hewn from played their part in stimulating the drill-and-blast method and parts and shafts with a challen- a single stone. a revival in underground cons- reinforced with rock bolts and ging design or poor rock quality During the Industrial Revolu- truction. shotcrete. are also modelled in at least 2-D. tion of the nineteenth century, The waves of rock enginee- The results from the rock mecha- society discovered the benefits ring follow and complement one 1.1 Site investigations nical simulations are used, too, of underground construction in another. Infrastructural under- The facilities will be located in to guide building projects in the connection with urbanisation. ground facilities such as metro the hard bedrock composed of vicinity of the metro line. This led to the second wave of systems and various enginee- Precambrian granite and various In Keilaniemi, four 100 m tall rock engineering, when under- ring tunnels and caverns have kinds of gneisses. These contain tower buildings are planned next ground caverns and tunnels not lost their relevance in larger zones with fractured rock, espe- to and above the metro line and were built to improve the com- cities. Similarly, the third wave of cially undersea and in the areas station. The foundation pressu- munity infrastructure, i.e. to ser- relocating recreational and cul- prone to settling, which from re of the buildings is between 2 ve as sewers, metro tunnels and tural facilities is also continuing. tunnelling point of view will be and 4 MPa for each. In these con- municipal engineering facilities. Now, inspired by concern for the challenging. ditions, it is vital to simulate the Military defence structures and natural and urban environment, The engineering geology of interaction between the tunnels power plant technology were the fourth wave is bringing the the area is studied for many years and the surrounding structures also essentially developed. experience of the rock enginee- in several stages. The whole de- in advance, so that the critical The third wave of rock engi- ring field to the fore as a timely sign process was started with the parts of the construction can neering involved the relocation alternative to traditional surface old survey data handed over to be identified and the design can of some human activities from construction [1]. designers, and new, more conci- then be optimised accordingly. the surface to underground case surveys programmed in areas It has to be confirmed that the verns. Sports halls, swimming 1 West Metro extension with wide tunnel spans or critical additional foundation loads on pools, ice hockey rinks, and per- The west metro will be an ex- geological conditions. the surface will not damage the manent art exhibitions exemplify tension of the existing Helsinki tunnels and, on the other hand, the range of the recreational and metro line to the city of Espoo. 1.2 Detail design stage that the tunnels will not cause cultural applications then under- This fully automated line is esti- The decision to begin construc- unacceptable displacements taken. The business community mated to be opened for traffic tion at the end of year 2008 set in on the foundations of the struc- also brought underground pe- at the end of year 2015. It will motion an intensive implemen- tures above. 3-D modelling is 20 Tunnelling Market in Finland Tunnel 3/2011

therefore required to reach the a giant multidimensional rail mechanical analysis are done in platform areas and in escala- precision required, when working tunnel system of Ring Rail Line. using 3DEC-program and criti- tor shafts of the underground with such variable shapes and load The tunnel system consists of 4 cal key blocks are analysed using stations and evaluate the maxi- distributions. underground rail stations with Unwedge-program. mum pressure loads against tun- access tunnels, pressure equali- nel doors and glass structures in 1.4 Excavation design zation and smoke removal shafts, 2.2 Aerodynamic simulation the stations. The excavation design is bon- vertical exit shafts, connection The aerodynamic simulations The station with the high- ded to a beforehand chosen tunnels at 200 m intervals, rail ex- were carried out in 2 steps. The est identified air speeds in the standard profile (Fig. 2, 3). The change areas and heat transfer complete tunnel system was escalator shafts was simulated dimensions for the track tunnel tunnels in portal areas. simulated using 1-dimensional in 3-D to account for the 3-di- are, on the other hand, based transient fluid dynamics code mensional flow effects and high- on space requirements of the 2.1 Rock mechanical IDA Tunnel. The code solves light the areas with the highest metro train and its rail system simulation the aerodynamic flows occur- velocities. The air flows from/to plus an additional 1200 mm for Rock mechanical analysis is ring in the tunnel network due the adjacent tunnel sections ob- an emergency exit lane. In the needed to predict structural train motion and thermal or tained from 1-dimensional simu- parts where the tunnels cross the behaviour of rock mass and to external influences governing lations were used as boundary sea, free space to build a water- determine right location and po- incompressible fluid flow equa- conditions for the 3-D studies. pressure-proofed construction is sition and needed reinforcement tions in 1-D. The 3-dimensional The 3-D simulations were carried reserved in the excavation pro- procedures of underground faci- effects of the flow are modelled out using the commercial CFD file. Furthermore, a large amount lity. In Ring Rail Line all 4 under- using pressure loss coefficients software package ANSYS CFX. of grouting and reinforcement ground stations are simulated and friction factors as in nor- Simulations in the early phase profiles for a wide range of dif- using interpreted geometrical mal practise for transient 1-di- showed that the highest air ferent geological conditions are and mechanical model of rock mensional pipe flow networks. speeds are found at Ruskeasan- needed in addition to the exca- mass. Rock mechanical simula- Different tunnel system layouts ta station (Fig. 5) and therefore vation profiles. tions showed the critical areas and changed tunnel profiles it was chosen to be modelled in which need extra reinforcement have been investigated in 1-D 3-D. As well as highest observed 2 Ring Rail Line procedures and stability super- with various train timetables to speeds in escalator shafts, Ruske- The Ring Rail Line is an important vision during construction. Rock determine the peak air speeds asanta station has the disadvan- circular rail route of the Helsinki West metro line Metropolitan Area. It is an urban two-track passenger line for lo- cal traffic in Vantaa between Vantaankoski and Tikkurila and a rail link from Helsinki to Hel- sinki-Vantaa airport (Fig. 4). The total length of the new line is 18 km, of which 8 km run in twin tunnels mainly under the Helsin- ki-Vantaa airport area. New SM5 low-floor trains will operate on the Ring rail Line at 10-minute intervals in both directions during peak periods. The maximum train speed will be 120 km/h. Construction of the Ring Rail Line began in spring 2009 by tunnel excavations using drill and blast method. The line will be open for traffic in the middle of 2014 [3]. Computational simulations have been in key roles from 1 the beginning when designing Tunnel 3/2011 ITA/WTC 2011 in Helsinki 21

tageous situation of 2 escalator 2.3 Fire simulation shafts which differ in length by The fire scenarios are dimensioned a factor of 2. The pressure drop by operating train and modelled caused by a shorter escalator using the geometry of the com- shaft is much smaller than the plete tunnel system. Two different one caused by the longer shaft. fire scenarios were simulated with The differences in the air veloci- 1-dimensional software IDA Tun- 2 ties are substantial. nel to generate boundary condi- In Ring Rail Line the train tions for detailed 3-dimensional Metro tunnel profile schedule was noticed to have a analysis. The worst case fire loca- significant influence to air flows tion in the tunnel section with and pressures in escalator shafts highest slope between Viinikkala and access tunnels. Air speeds and Aviapolis station was chosen can reach up to 7.5 m/s for very to be simulated. short periods. The maximum The 1-dimensional simulati- speeds are found at the start ons show that ventilation system of the daily service when trains is capable to produce air speed enter the tunnel system. During of approx. 3.5 m/s in the tunnel regular operation the peak air section in question. This velocity speeds are approx. 6.0 m/s. The is higher than the critical value simulations show that the maxi- to prevent smoke back-layering mum air speeds are localised and for the corresponding fire power only occur a very limited time. As of 40 MW. 3 regulations allow the air speeds The 3-dimensional Compu- to increase to a maximum of tational Fluid Dynamics (CFD) Metro station profile 10 m/s in rare cases, the present simulations show that the smoke design of the tunnel system is propagation in the first minutes time passengers need to exit tum). One PWR unit (1600 MWe) assessed to be acceptable. after the start of fire is guided tunnels or stations to the safe is under construction at Olkilu- by the initial air movement. side. According to exit simulation oto [4]. Depending on the fire location the interval of cross connecting According to the Nuclear En- the turbulence of the air flowing tunnels between rail tunnels ergy Act, all nuclear waste gene- around the train can destroy the was designed to be 200 m. The rated in Finland must be handled, natural stratification of the hot passengers of the whole train stored and permanently dispo- smoke and cause a decreased are simulated to exit through sed of in Finland. The 2 nuclear visibility in the complete tunnel connection tunnels to the safe power companies, TVO and For- cross-section. side in 6 minutes in a tunnel sec- tum, are responsible for the safe In both scenarios the tem- tions. The simulation showed in management of the waste and peratures in a rail tunnel along the stations that escalator shafts for all associated expenses. TVO the path towards the fire loca- and upper levels of the station and Fortum established a joint tion will be less than 70 °C at all should be fire-compartmented company, Posiva Oy, in 1995 to times. As soon as the ventilation from the platform level to allow implement the disposal program system is running at full power, exit to the safe side. for spent fuel. all the smoke produced by the Preparations for nuclear waste fire will be pushed towards the 3 Spent nuclear fuel management were commenced smoke removal shafts. storage in Finland already in the 1970’s The Finnish nuclear power when the power plants were still 2.4 Evacuation simulation plants have been in operation under construction. In 1983, the The smoke propagation and eva- for more than 25 years. Two BWR Government confirmed a target cuation simulation of Ring Rail units are operated at Olkiluoto schedule for spent fuel manage- Line were done with Fire Dyna- (2 x 860 MWe) by Teollisuuden ment, in which the construction mics Simulator (FDS) and FDS- Voima Oy (TVO), and 2 PWR of the final disposal facility was Evac software. The evacuation units at Loviisa (2 x 488 MWe) by scheduled for the 2010’s and the simulation presents how much Fortum Power and Heat Oy (For- start of final disposal for 2020. 22 Tunnelling Market in Finland Tunnel 3/2011

Ring rail tunnels

Potential sites for the disposal should be possible later to link 420 m. The deposition tunnels An underground rock characteriza- of spent fuel were screened al- the ONKALO to the repository so and deposition holes drilled in tion facility, ONKALO, is excavated ready in the 1980’s, followed by that they are integrated. Excava- their floors are collectively called at the disposal level. ONKALO has detailed site investigations in the tion work for ONKALO began in the repository. The spent nuclear been designed so that it can later 1990’s and an environmental im- September 2004. fuel is deposited in the reposito- serve as part of the repository. The pact assessment in late 1990’s. In Olkiluoto site has ready in- ry. Connections to the ground first part of the disposal facility will 1999, Posiva submitted an appli- frastructure built for the nuclear level from the disposal facility are be excavated after the construc- cation for a Decision-in-Principle power plants. One reactor is also via the access tunnel running at tion licence phase in the 2010s, (DiP) to choose Olkiluoto as the under construction. For the de- a slope of 1:10, and via 5 verti- and operations will start in 2020. site of the final disposal facility. sign of above ground facilities cal shafts. Shafts are a canister The fuel from 4 operating reactors The Government issued a DiP in this meant that several buildings shaft, a personnel shaft, an inlet as well the fuel from the fifth nuc- favour of the project in Decem- and systems exist already and air shaft and 2 exhaust air shafts. lear power plant under construc- ber 2000, and the Parliament rati- these are not needed to cons- A layout example of the disposal tion has been taken into account fied the decision in May 2001. truct. For underground disposal facility is shown in Fig. 7. in designing the disposal facility. facility this meant that the con- 3.1 Site selection nections to above ground must 5 Investigations, characterization fit in existing infrastructure, and more detailed design could roads, power lines etc. now be focused into one site. A decision was made to excavate 3.2 Outline design an underground rock characte- Outline design of the Disposal risation facility, ONKALO, at Olki- Facility was developed during luoto. The ONKALO facility shall 2008 to 2009 and published in be constructed in such a manner 2010. The disposal facility con- that it allows further characte- sists of surface connections, risation and research work (Fig. technical rooms at an approx. 6) to be carried out without jeo- level of -437 m, the central tun- pardising the longterm safety of nel network and the repository the repository site. In addition, it facilities at an approx. level of - Air velocities at Ruskeasanta station Tunnel 3/2011 ITA/WTC 2011 in Helsinki 23

Research niche 29 The amount of spent nuclear fuel to the specified minimum dis- T 28 T 27

is 5550 tU. The disposal facility is tance, a total of 80 tunnels will T 26 excavated and closed in stages be required. The total length of T 25 over the long operational time of all deposition tunnels would then T 24 T

about 100 years. be about 28 km. In practice, the 23 T 22

The disposal canisters are depo- total number and total length of T 21 sited in holes drilled in the deposi- deposition tunnels will be greater T 20 tion tunnel floors. The holes have than that. Due to reasons related to T 19 T 18

a diameter of 1.750 mm, and their the bedrock, all deposition tunnels T 17 depth is 7.80 m for OL1-2 canisters, cannot be of the maximum length, T 16 8.25 m for OL3 canisters and 6.60 m nor can the distance between de- T 15 for LO1-2 canisters (Fig. 8). position holes always comply with T When the deposition tunnels the specified minimum distance. Innovativer – Kompetenter – Zuverlässiger are located at distances of 25 m The total volume of the disposal from each other, the minimum dis- facility is approx. 1.1 million m3. tance between deposition holes The maximum open volume is Gemeinsam stärker is 9.0 m for OL1-2 canisters, 7.2 m around 0.6 million m3, because for LO1-2 canisters and 10.6 m the disposal facility is excavated im Tunnelbau for OL3 canisters. The maximum and backfilled in stages. length of deposition tunnels is The disposal facility is divided Schläuche · Armaturen · Zubehör für: hoses · fittings · equipment for: limited to 350 m for reasons rela- into a controlled area and an ted to ventilation technology and uncontrolled area. Canisters are Pressluft compressed air occupational safety. always handled and lowered to Wasser water A total of 2820 disposal canis- the deposition hole in the con- Beton concrete Salweidenbecke 21 ters will be required for this quan- trolled area. The excavation and 44894 Bochum, Germany tity. In an optimal situation where construction of new tunnels and Tel. +49 (0)2 34/5 88 73-73 all deposition tunnels are 350 m the backfilling of the tunnels is Fax +49 (0)2 34/5 88 73-10 [email protected] long, and the distance between carried out in the uncontrolled TechnoBochum www.techno-bochum.de deposition holes is always equal area. Extensive material trans- 24 Tunnelling Market in Finland Tunnel 3/2011

Spent nuclear fuel repository layout

fers, such as transfers of excavated rock and backfill materials, are done in the access tunnel. Separate ventilation systems are provided for the controlled and the uncontrolled area. When all the canisters have been disposed of in the deposition holes and operating and de- commissioning waste from the encapsulation plant has been disposed of, the closure phase of the repository will begin. The structures and the systems of the repository are first removed so that no harmful amount of materials is left in the repository. After that the rooms are backfilled and sealed with closure structures.

4 Conclusions 8 Underground construction is Release barriers an essential part of modern and responsible environment References construction. It can be applied [1] Finnish Tunnelling Association (1997). The Fourth Wave of Rock Construction, eds. Rönkä, K. and Ritola, J. grobally to help solve the pro- Maanaklaisten tilojen rakentamisyhdistys ry, Helsinki. 137 p. [2] Salmelainen, J., Westerlund, G., Ström, J. and Roinisto, J. (2011). The west metro – the design of rock structures blems involved in developing in project and construction planning. Proc. World Tunnel Congress, Helsinki. 7 p. (Approved for publication) and improving communities. [3] Vuopio, J. and Inkala, M. (2011). Ring Rail Line – Modern methods in design of the tunnel system. Proc. World Rock construction literally adds Tunnel Congress, Helsinki. 8 p. (Approved for publication) [4] Palonen, E. And Saanio, T. (2011). Design of the spent fuel disposal facility in 1990 and 2010. Proc. World a new dimension to community Tunnel Congress, Helsinki. 10 p. (Approved for publication) development [1].