Moutier Tunnel Breaks Through during Saint Barbara DayThe Moutier tunnel holed through on Monday 4th December, 2006 after a mass celebrated in honor of Saint Barbara, the patron saint of miners. The downhill tube has holed through three years after work commenced. In February 2003, the 2,000-tonne TBM, which began drilling in end October 2002, could not progress any farther and had to stop in a geologically disrupted zone. Tunnelling then continued in the parallel tube, using traditional methods, and then in the downhill tube. Currently, work in on schedule, so that the entry in service of the 1.2 km tunnel is programmed for fall 2011. Five years after work commenced, the breakthrough is a very important milestone marking a major step toward completion of the tunnel. The north teams have made the junction with the south teams, boring the tunnel in six steps. The two upper and lower sidewall tunnels are completed. The teams have made their way through in the two upper sidewall tunnels. Given the complicated geology of the subsoil crossed by the Moutier tunnel and the difficulties caused to work so that the project could not go smoothly since 2003, all the project players have shown fair play to resolve the problems. The contractor is Groupement du Tunnel de Moutier (GTM), including Marti Tunnelbau, Marti Bern, Pro Routes, Parietti et Gindrat, Marti Travaux Spéciaux and Georges Chételat. Indeed, construction began in June 2001 with ground investigation work at the two tunnel portals. The TBM assembly then follows during 2002. The machine is ready at fall 2002, and the cutting wheel begins excavation on 31st October, 2002. Four months later, on 27th February, 2003 the TBM is stopped, after less than 200 metres of advance in the downhill tube. The stoppage was caused by a tricky geological zone that preliminary geological surveys did not identify. A completely unforeseen collapse of the face occured, which caused a sinkhole visible at the surface. The impressive tunnel boring machine of more than 2,000 tonnes is at a standill for some time. Immediate measures are taken to consolidate the ground and restart the machine but they are little efficient and fail to reach the objective. Tunnelling resumes in May 2003 in the uphill tunnel, by means of traditional methods. Meanwhile, engineering firms, the contractors and the project owner look for another solution for the continuation of the tunnel project, while geologists drill complementary boreholes. At spring 2004, further to studying several alternatives, the owner proposes a solution to the federal roads office (OFROU), who approves it. The selected solution advocates that the TBM follow its path towards the Eschert portal. Before its restart, the top heading of the tunnel is driven from the north portal.At about 150 metres ahead of the TBM, the tunnel crosses a critical zone with tectonised marls, identified by the additional ground surveying. In this zone, which crosses obliquely the two tunnel tubes, the ground is so unstable that the circular cross section of the tunnel can only be excavated in six phases to guarantee safety in the tunnel and protection of workers. This zone is completely excavated and supported before the TBM can progress any farther. At the end of 2004, the contractor is invited to bid for a supplement to the contract, established on the basis of the new tunnel construction project. In early 2005, GTM submits its complementary bid to the owner. After a thorough assessment and negotiation phase between the owner and the contractor, a supplement to the contract is signed between the two parties in July 2005. During this phase, work continues without interruption. During most of 2005, the tunnel is driven from five attacks. The top heading of the tunnel is excavated in both tubes, from north to south. From south, two crews advance to the north, while a third crew progresses towards the TBM after reaching a crosscut between the two bores to drive back in the downhill tube until reaching the cutterhead. The cutterhead is reached in September 2005. Shortly after, in October 2005, a test of the machine is performed successfully. To the great satisfaction of all parties, the TBM moves forward by 18 metres between end 2005 and early 2006 to leave the zone where it stayed motionless. The machine works and will tunnel again when sequenced excavation through the tectonised marls is finished. Visit www.herrenknecht.comHowever, there is still a lot of work to do. The next excavation work is two cross passages between the two tubes and the last two sequences among the six phases of the divided cross section in the tectonised marls. Then, it will be necessary to dig the lower part of the tunnel (benches and invert), using traditional methods early next year in the uphill tube, and with the TBM as from mid 2007 in the downhill tube. When all tunnelling is completed, the finishing stage and equipment of the tunnel will have to be done.The upper halves of the two tunnels are excavated and supported. The uphill tube has in fact nearly holed through. Therefore, the project is subject to little geological uncertainties. Predictions for the lower sections can be calculated fairly precisely from the observations performed during excavation of the top headings. The quantities of materials used so far to reinforce the tunnel are impressive and give a clue of the geological conditions encountered: 4,000 tonnes of steel arches, 55,000 metres of steel pipes for forepoling, 45,000 metres of rock anchors and 50,000 cubic metres of concrete. Regarding the tunnel costs, the works performed since the TBM stoppage up to now are part of the new contract. The tectonised marl zone is actually slightly longer than planned, but includes rocks and soils slightly better than foreseen. From the north, faster advances than those set in the contract allow to compensate reinforcements more important than previously thought. Given the work advance in the last three years, the contractual schedule that predicts the completion of the scheme in 2011 will be fulfilled. Click ch/30. Read E-News Weekly 41/2005, 16/2005, 37/2004, 13/2004, 32/2003 & 35/2002. Visit www.a16.ch/a16/comm/061204_tu_mou_percement.htm and www.transjurane.net 50/06.