First Breakthrough at Gotthard Base TunnelConstruction workers made the first breakthrough at the Gotthard base tunnel on 6th September, 2006 in what will be the world's longest rail tunnel, meeting under the Swiss Alps. The breakthrough linked the 15.9 km southern stretch of the Gotthard rail tunnel with an intermediate section to the north. Engineers and miners from the TAT consortium (lot Bodio 554), including Implenia (the merger of Batigroup and Zschokke Locher), Alpine Mayreder, CSC, Hochtief and Impregilo, worked from the south portal in Bodio using a Herrenknecht hard rock TBM (machine S-210) and made the breakthrough in the east bore to meet at Faido with colleagues boring to the north from the multi-function station. Workers climbed through a small gap between the two tunnel sections of the new Gotthard link and waved national and local flags in celebration. More than 1,000 people witnessed the breakthrough. The two bores met almost exactly, with a discrepancy of just 2 cm vertically and 5 cm horizontally. The deflection on 100 metres does not exceed 1.5 mm. Such accuracy has been maintained from the south portal to the Faido multi-function station, i.e. on a distance of nearly 16 km. Seven other breakthoughs are scheduled in the years to come because tunnelling on the twin bores started at five different places, namely the south and north portals (Bodio and Erstfeld), two multi-function stations (Faido and Sedrun) and Amsteg. There will be 16 drives altogether. Visit www.herrenknecht.com and www.tat-ti.ch The 8.83 m-diameter Gripper TBM started boring the east tube in January 2003. The second TBM started on the west tube one month later. Click here. Several difficult geological areas had to be overcome on the 13.9 km segment to the Faido multi-function station. The changing geology slowed down tunnelling. The TBM has a power of 3,500 kW and measures, including all the trailing gear and backp-up equipment, more than 400 metres. To secure the rock, crews install sprayed concrete, anchoring bolts, welded mesh and steel arches. A breakthrough in the second, west tube on the same section is expected next month. Cross passages are blasted every 325 metres. For excavation of the two main tunnels under the Gotthard between Faido and Sedrun, the two TBMs will be entirely revised. The diameter of the cutterhead will be extended to 9.4 m. The TBMs will be transported across the multi-function station in Faido and will get back to work to drive the approx. 11 km section towards Sedrun, where the arrival is expected in 2010. Preparatory works in Bodio began exactly seven years ago, in the autumn of 1999. Since then, 28.7 km of tunnel has been dug from Bodio by means of TBMs and almost 6 km by drill and blast. The 35 kilometres of tunnel excavated altogether at the Bodio site represent more than a third of the 99 km driven to date. In addition, 22 km of tunnel has been lined. These are the first and unique kilometres to be lined up to now at the Gotthard base tunnel. Miners of various nations celebrate the first breakthrough of the east tunnel of the Gotthard base tunnel at the multi-function station in Faido, Switzerland on 6th September, 2006 Not many days after the commencement of tunnelling in the east tunnel, the TBM shield unexpectedly encountered squeezing rock on 17th February, 2003. The weight of the rock put extreme pressure on the machine. Crews had reached a geological fault, a rock stripe entirely weathered and cohesionless, that ran almost in parallel with the tunnel path for more than 500 m. Thanks to the excellent collaboration between the designer, contractors, construction management and owner, the adecuate technical solutions have been found. Later on, for many kilometres the problems were just "manageable routine", with detachments of rock blocks of a certain size, similar to what had already been encountered during excavation of the Polmengo pilot tunnel. Such events were gradually managed. The last kilometre before the breakthrough in Faido is also particularly difficult because, unlike what the geological information previously available said, squeezing rock "pushes", which means that it tends to close the bore just excavated. Sometimes, the deformations occur too quickly for the TBMs such that it is impossible to avoid stoppage. There was a case when these phenomena brought the TBM to a standstill, the machine being literally caught into the grip of the mountain. Two weeks were necessary to release the cutting head of the TBM and resume tunnelling. In other cases, specially where the rock is harder, miners can even hear in the Bodio tunnels "bangs of the mountain", i.e. strong noise that burst simultaneously with the release of tensions in the rock mass. When the first Gotthard rail tunnel was constructed from September 1872 to February 1880, miners achieved advances of 5.5 metres a day. Around 2,500 workers were then employed for seven years to tunnel 15 km approximately of the old rail tunnel. The two drives met with a discrepancy of 33 cm horizontally and 5 cm vertically. With the means used at that time, that was brilliant masterwork. The TBMs of the XXIth century excavate 24.2 metres of rock in 24 hours. In December 2005, the machine in the east tunnel even beat a record with 38 metres drilled in a single day. At full speed, 600 people have been employed 24 hours a day, seven days a week. On Saturday 16th September, 2006 the public is invited to visit the construction site in Faido at an open day to admire the TBM.The new 2 x 57 km Gotthard rail tunnel is far deeper than the existing 15 km tunnel link. Journeys are slowed by trains having to climb to each entrance. The original Gotthard train tunnel guides more than 200 passenger and freight trains through the mountain each day. In 1980, the 16 km Gotthard road tunnel opened. But chronic holiday traffic jams, lorries lined up for kilometres on either side of the tunnel and freight trains needing three locomotives just to mount the steep grade confirm that the network is overloaded. With the new tunnel, the existing route will be shortened by 40 kilometres and fundamentally flat, which means faster trains, shorter travel times and a freight capacity that is more than doubled.The Gotthard base tunnel is the vital link on the new Gotthard railway, which is part - together with the Loetschberg base tunnel - of a wider project to upgrade north-south links under the Alps, the so-called New Rail Links through the Alps (NRLA). For its optimal operation, the construction of the Zimmerberg and Ceneri base tunnels is fundamental together with their commissioning in parallel with the Gotthard base tunnel. Thanks to the Zimmerberg and Ceneri base tunnels, the new link will become a plain railroad bringing many economical and ecological advantages. In Switzerland, about 3 million people will benefit from the project. If we add the bordering regions of south Germany and Lombardy, the ridership area extends to 20 million people. When completed in 2016, the tunnel will cut Zurich-Milan journey times by an hour compared to the existing line.Funds for the Gotthard base tunnel are allocated from petrol and sales tax, loans (only 15%) and just over half from freight tax. At the Bodio jobsite, AlpTransit San Gottardo has invested so far CHF903 million. The estimated cost for the Gotthard base tunnel is CHF8 billion. The most recent estimate for the entire NRLA programme is CHF17.8 billion, up from CHF10.1 billion in 1990. Click here. Read E-News Weekly 4/2005 & 41/2004.On 1st September, 2006 advance at the Gotthard base tunnel had reached 98.76 km or 64.3% of the total system of 153.5 km of tunnels, galleries and cross passages. The total distance driven in August 2006 was 944 metres. Around 2,200 miners and engineers work at all the Gotthard sites. Today, some 1,000 people from Switzerland, Germany, Italy, Austria, Portugal, Bosnia, Croatia and other countries work at Bodio and Faido. Click ch/17, ch/20 & ch/21. To read about the Sedrun section, click here, here, here, here and ch/22 and see E-News Weekly 43/2005 & 29/2005. To read about the Amsteg section, click here, here and ch/19 and see E-News Weekly 29/2006, 48/2005, 49/2004 & 46/2004. To read about the Ertsfeld section, click ch/52 and see E-News Weekly 9/2006. Visit www.alptransit.ch 37/06.