Tunnelling of Lausanne Metro Nears EndLine M2 of the Lausanne metro in Switzerland, between Ouchy and Croisettes, consists in building a new section between Flon and Croisettes and upgrading the existing section between Ouchy and Flon. The 6.4 km line will have slopes averaging 5.7% with a maximum point reaching 12% to climb an elevation difference of 340 metres.In 1877, a funicular single-track line (1,164 m) opened to connect Ouchy along Lake Geneva to Flon in the city centre. A special funicular shuttle service (318 m) between the central railway station (Lausanne CFF) and Flon using a separate track in the same tunnel between these two stations opened in 1879. The entire line (1,482 m) was converted into a cog railway in 1954. Operation of this cog train ended on 22nd January, 2006. The Ouchy-Flon section will now be upgraded and double-tracked to be connected to the new Flon-Croisettes section, thus providing a new automatic driverless tyred metro between Ouchy and Croisettes. Section Flon-Croisettes consists in building 2,884 metres of bored tunnels (contracts 1200, 1300, 1400, 1500, 1700 and 1900) and 260 metres of cut-and-cover tunnels (contracts 1400, 2000 and 2100). These lengths do not include the underground stations. To date, 94% of the tunnels are completed. Tunnelling is scheduled to end next summer. The first tracks have been laid at the Vennes depot in December. Opening of the line is programmed for the end of 2008. The bill amounts to CHF716 million.The tunnelling method has required a fleet of two small Voest Alpine AM50 roadheaders for tunnelling in top heading and bench sequence (contracts 1300 and 1400) and five big Eickhoff roadheaders (contracts 1200, 1400, 1500, 1700 and 1900) for full section tunnelling. The cut-and-cover method is used for building the stations, except the Place de l’Ours and Bessieres stations (built in top heading and bench sequence) and the Fourmi station, built from a deep shaft in a cavern excavated in divided sequence horizontally. Visit www.vab.sandvik.com and www.eickhoff-bochum.deThe geology is composed of molasse, marls and sandstone. Tunnelling takes place in majority in loose ground, generally dry but sometimes saturated with water. All the spoil is mucked away by loaders and dumpers. All the material is reused in La Sallaz (valley) for landscaping purpose and stored at a dump site between Vennes and Croisettes in Epalinges.The support consists of 15-20 cm of steel fibre-reinforced shotcrete, HEB steel arches, lattice girders, Swellex and other bolts and Sika Master Seal 345, a sprayed waterproofing product. Sika Master Seal 345 replaces PVC waterproofing liners. It is the first time that such a product is applied at large scale at a tunnelling worksite. Since its implementation is faster than installing a PVC waterproofing liner, this method should be a cheaper solution. There is no final concrete formwork except 136 metres in contract 1300 (Langallerie tunnel) where 15-20 cm of shotcrete, a PVC waterproofing liner and a concrete formwork have been installed due to the presence of water. Visit www.swellex.com and www.sika-stm.comContract 1200 (306 m-long Saint-Laurent tunnel between Flon and Riponne stations and 272 m-long Viret tunnel between Riponne and Bessieres stations) is built by AOC (Association Ouchy-Croisettes), a JV of Deneriaz, Zschokke Locher, Grisoni Zaugg and Walo Bertschinger. The Saint-Laurent tunnel under Saint-Laurent Square collapsed in February 2005 (read E-News Weekly 10/2005). In July 2005, tunnelling recommenced from Riponne to Saint-Laurent Square. Excavation of the last 30 metres under Saint-Laurent Square started in February. Prior to excavation with the roadheader, the face is reinforced with glass-fibre rods and a rigid roof of steel pipes. This double technique combining canopy of steel pipes around the vault and glass-fibre rods at the face will have to be repeated three times to cover the distance between the face driven downwards and the curtain of piles installed after the collapse. More than seven months will be necessary to complete these last 30 metres.Further to the collapse at Saint-Laurent, it was decided to drive the Viret tunnel 3.5 metres deeper in the molasse. The consequence for trains will be an added gradient of 12% instead of 5% to reach Bessieres bridge. Breakthrough of the Bern Road tunnel Contract 1300 (136 m-long Langallerie tunnel and cutting through the pillars of Bessieres bridge) has been awarded to Losinger and Frutiger. The Langallerie tunnel is the most expensive of the M2 project, at CHF100,000 per metre. Tunnelling in a top heading and bench sequence has been adopted due to water-bearing ground with poor cohesion and high compressibility. Instead of full section tunnelling, which would increase the risk of collapse, crews excavate two small parallel tunnels, at the right and left handsides of the future 136 m tunnel. These sidewall tunnels measure approx. three metres in width and four metres in height. Once tunnelling is complete, the walls are concreted to shape stiff supports for the top heading of the main tunnel. Then, back to the starting point, crews drive the top heading (the upper part of the tunnel) above the two sidewall tunnels already completed. The next stage is the excavation of the middle bench between the two sidewall tunnels and the last phase is the invert, ie. the bottom of the tunnel. The tunnel is therefore built in four stages. The face and crown of the sidewall tunnels are treated with jet grouting, by injecting prior to excavation a high pressure cement grout into the ground. Then crews dig in this solidified aggregate. The same technique is employed to drive the tunnel crown. Six months are necessary for the sidewall tunnels, another six months for the remaining phases and therefore a full year will be needed since tunnelling started in June 2005. The Bessieres and Ours stations are also excavated using this methodology.The construction of a viaduct through the pillars of Bessieres bridge was a world first. A 7 m-wide x 5 m-high tunnel has been cut through the two pillars. Firstly, a canopy of steel pipes has been constructed, introducing steel bars through the pillar above the future excavation, to avoid any subsequent collapse of material. Then, the pillar has been reinforced with steel anchors, a bit as if pins were introduced to mark into squares the part of the pillar to be excavated around the driveage axis. Above this axis, ten transversal holes have been drilled to insert reinforcement cables. This is only then that drilling could commence using a pneumatic hammer. Numerous vibration and fissure sensors have been installed to monitor the stability of the bridge.Contract 1400 (161 m-long cut-and-cover tunnel at the federal Court and 67 m-long Perdonnets tunnel between Bessieres and Ours stations, 486 m-long Bugnon tunnel between Ours and CHUV stations) is built by Prader Losinger, Murer, Losinger, Deneriaz Sion and Frutiger. The cut-and-cover tunnel is finished.The Bugnon tunnel has holed through on 14th March, 2006. Only 6% of the tunnels then remained to be excavated. In the lower part of its route, tunnelling of the Bugnon tunnel was undertook in good molasse. However, near CHUV station, soft ground required the construction of umbrella vaults.Contract 1500 includes the Falaises tunnel (503 m) between CHUV and La Sallaz stations. The tunnel holed through on 13th July, 2005. It was the first breakthrough after ten months of work, two month ahead of schedule. The builders are JPF Construction, Induni, Evequoz and Getra. A 2.5-tonne Indeco HP4000 hydraulic breaker mounted on a Liebherr R934 excavator worked in the CHUV tunnel in close proximity to Lausanne's major hospital. The tunnel is not straightforward as it combines a curve with a steep gradient. Visit www.indeco-breakers.com and www.liebherr.com/me/en/default_me.aspContract 1700 (662 m-long Bern Road tunnel between La Sallaz and Fourmi) broke through on 17th February, 2006. This contract connects with contract 1900 at Fourmi station, thus forming a 1.2 km tunnel between La Sallaz and Vennes. The constructors are Marti Tunnel Bau, Marti Travaux Speciaux and Batigroup.Contract 1900 (452 m-long tunnel of the highway between Fourmi and Vennes) was completed on 16th September, 2005 by Infra Tunnel (an affiliate of Spie Batignolles) and Losinger. The first 120 metres crossed soft ground, which required to install 11 sets of steel pipe roofs to consolidate the ground. The remaining length of the tunnel (3/4 of it) was dug in molasse without particular problems. The attack was descending. At that date, 65% of the tunnel was completed.Contract 2000 includes a cut-and-cover tunnel (30 m) built by Perrin Freres, Batigroup, Marti Travaux and Bertholet & Mathis. Contract 2100 has another cut-and-cover tunnel (68 m) built by JPF Construction. Click ch/36. Visit www.t-l.ch/m2 12/06.