Epoch-making Gotthard Baseline
Oct 2010
Herrenknecht AG News Release
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Breakthrough at the Gotthard Base Tunnel on October 15, 2010 in the eastern tunnel marks the most significant milestone on the way to completing the longest railway tunnel in the world. With the twin 57km long epoch-making project, Switzerland is connecting northern and southern Europe by rail through the Alps. After completion of the project, the four Herrenknecht gripper TBMs on the project will have excavated more than 85km of the main tubes.
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European links through Switzerland
- In 2017, the first high-speed trains will travel along, or rather through, the New Alpine Transversal (NEAT) mountain link at speeds of 200-250km per hour. This will cut the journey time from Zurich to Milan by one hour to 2 hours, 40 minutes. Swiss Railways are expecting, in particular, to cut freight transport times – yet another important improvement in traffic logistics between Germany and Italy. A new era in trans-Alpine rail travel is dawning.
- The international link is made possible by epoch-making construction of the new Gotthard Base Tunnel along with the Ceneri and Zimmerberg Base Tunnels. With a length of 57km and a maximum altitude of 550m above sea level, i.e. truly at the foot of the St Gotthard mountain, two single-track tunnel tubes will put an end to travel that was so slow and in need of double locomotives to drive freight trains up steep gradients and over the mountains in the past.
- "This will be a high-speed rail corridor for Europe straight through the Alps, to transport goods in an environmentally friendly way from Rotterdam to Genoa," said Moritz Leuenberger, Swiss Federal Councillor, in describing the 'longest wonder of the world'. "We are working together with our partners on developing Europe's infrastructure, even though we are not members of the EU," he continues. This truly great feat is part of Switzerland's plan to transfer as much freight as possible from road to rail as a way of protecting the environment.
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World record Gotthard Base Tunnel progress to the first main rail tunnel breakthrough on 15 Oct, 2010
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Gotthard Tunnels - Past, Present and Future
Tunnels have been built through the Gotthard-Range for more than three centuries. The Gotthard Base Tunnel will be the longest tunnel in the world - an epoch-making project of this time just as ealier ones were of their time. -
1707 The master builder Morettini from Ticino chipped and blasted a 64m long tunnel through the Chilchberg Mountain – it is known as the 'Urner Loch'.
1872 Construction of the first rail tunnel through the Gotthard begins, under the direction of the Swiss engineer Louis Favre.
1880 Breakthrough is achieved on February 29, with impressive precision for that time.
1882 The longest railway tunnel in the world at the time, with a length of 15km, goes into operation.
1969 Construction of the first road tunnel through the Gotthard begins.
1980 The first road tunnel is opened to traffic and connects Göschenen with Airolo.
1993 Exploratory drills begin at the Piora Basin.
1996 The first preparatory and exploratory work for the Gotthard Base Tunnel begins in Sedrun.
1998 The Swiss Government approves financing for the New Alpine Transversal (NEAT).
1999 Excavation activities begin in Sedrun with the first blasting works.
2001 The first machine orders are awarded to Herrenknecht.
2003 Tunneling work with the four Herrenknecht gripper TBMs begins.
2006 The Herrenknecht TBMs on the northern and southern sections of the Base Tunnel reach their first target –up to nine months ahead of schedule.
2008 The dreaded Piora Basin is successfully crossed by the TBM S-210.
2009 TBM tunnelling is successfully completed in the north.
October 15, 2010 Main breakthrough of the Gotthard Base Tunnel in the Eastern tunnel between Sedrun and Faido.
2017 The Gotthard Base Tunnel – the centerpiece of the new Alpine transversals – is scheduled to go into operation.
- The Alpine country is nearing this goal in leaps and bounds. The 'shell' of the world's longest railway tunnel is almost complete – the final and crucial breakthrough at the halfway point, the border between the Faido and Sedrun construction lots, took place on October 15, 2010. This will mark the completion of one of the most important stages in this spectacular undertaking, which has seen such impressive feats in its history. It is the result of almost half a century of intense planning and has evolved continuously along with technology and geological science. It has also required courageous and farsighted political decision-making. The idea of a Gotthard Base Tunnel was first voiced in 1947. Construction work did not begin until 2001.
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Giants in hard rock
More than 85km of the main tubes have been excavated and supported by four rock TBMs from Herrenknecht of Germany. The total 152km of tunnels and shafts and almost 180 cross passages on the project are divided into five construction phases and by three access points and supply caverns at the Gotthard giga site – at Amsteg in the north, at the Sedrun intermediate heading in the middle and at Faido in the south. Access is also afforded via the tunnel portals near Bodio in the south and Erstfeld in the north. Access at Amsteg is a 2km long adit while the access tunnel at Faido is 2.7km long and on a 13% downhill gradient. Access at Sedrun is via two spectacular shafts of about 800m deep. -
High-precision planning and geological imponderables
Surprises can always occur when excavating tunnels the size of the Gotthard project. It is not for nothing that tunnel constructors have great respect for their task.
- Their work is a tightrope walk between the highly planned and the unforeseeable. In spite of the many preparatory investigations, unexpected difficulties can always occur. For example, at the very beginning of tunnelling from the southern side of the Gotthard in February 2003, after only 200m, work was interrupted by unconsolidated rock. The two TBMs that set off from Bodio encountered geological disturbance zones known as kakirite zones. Such geological conditions are too soft for gripper TBMs. The rock machines could not leave these disturbance zones behind them until August 2003, after about 400m of very difficult tunnelling.
- But a construction log can also include unexpected positive reports. For example, there was good news from the northern side in spring 2004. In the construction plan the geologists had predicted a tunnelling interruption of up to four months to deal with the Intschi zone. Luckily, however, this zone was around 50% shorter than expected, and the teams operating the machines were able to pass through the zone, albeit with reduced tunnelling speed. That said, however, the ups and downs in the mountain seemed endless. Good monthly tunnelling performances of 560m and penetration rates of up to 12mm per revolution were followed by difficult stretches, some with a penetration rate of only 3mm per revolution and an advance of only 140m per month.
- There was bad news for the engineers and clients in June 2005. Suddenly and without warning, loosened rock mixed with mountain water infiltrated TBM Gabi 2's cutterhead in the western tube from the Amsteg access adit. At first, the tunnellers tried to clear the cutterhead of the fine material by hand and back up the TBM a few centimeters. Without success. Eventually, the unconsolidated area ahead of the machine's cutterhead was solidified by injecting it with a mixture of cement and bentonite. At the same time, the tunnel builders excavated a 50m tunnel from the east tube to the west tube to free the TBM's cutterhead from the front. Regular tunnelling was not resumed until November 2005 after a standstill of five months.
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Facing and overcoming the consequences of geological uncertainties
- The machines also had to deal with changeable geological conditions in the south on the stretch from Bodio to Faido. Noticeable improvements were attained by adapting the two TBMs to the unforeseen circumstances. In December 2005, TBM Sissi achieved the best daily performance in the Gotthard Tunnel so far of 38m in 24 hours in the east tube.
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2006 – the year of first breakthroughs
In June and October 2006 the construction teams in the north celebrated the end of tunnelling in the Amsteg – Sedrun section with a spectacular performance. The machines sped towards the end of the construction lot six and nine months ahead of schedule, respectively. But it all ended with an anticlimax. Just before the end of the lot they met with a geological obstacle – kakirite. This is why the TBMs were dismantled in advance in the solid rock zone. The workers then transported the machine components back out of the tunnel.
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Progress data for the North section TBM attach
- In fall 2006, breakthrough was finally made in the south, too, with the required precision at the Faido multifunctional station. The TBMs with diameters of more than 8m reached their targets after 13.5km and 14km respectively, with vertical and horizontal deviations of only a few centimeters. This degree of accuracy is comparable to a marksman hitting a 1 Euro coin at a distance of two kilometers. After a total overhaul and the fitting of new, larger 9.8m cutterheads, Sissi and Heidi set off again in July and October 2007, from Faido towards Sedrun.
- Safe passage through the Piora Basin
A further difficult zone awaited the tunnellers on the Piora Basin stretch - a funnel-shaped formation filled with sugargrained dolomite and water, which reaches deep into the rock of the mountain range. Its existence was long known, and hardly any other part of the Gotthard had -
Progress data for the South section TBM attach
- been investigated as intensely prior to the construction work. Since no one knew how far into the mountain the funnel reached, a decision was taken to make exploratory drills. In 1996, a 5.5km long exploratory tunnel was excavated to intersect this zone. The loose grains of rock turned out to be exposed to the enormous pressure of around 150 bar. A thick jet of water mixed with dolomite shot out of the mountain and flooded the road. The media called it ‘D-Day at Piora Beach'.
- A series of 19 inclined drills were made from the exploratory tunnel to the vicinity of the future base tunnel, finally giving the engineers the all clear. They hit on hard rock with no water pressure. Examining drill cores, temperatures and seismic results brought the geologists to the conclusion that the bottom of the Piora Basin was sealed with gypsiferous cap-rock.
- And so, on October 12, 2008, TBM Sissi reported: 'Piora Basin is successfully crossed', and its sister machine soon followed suit.
- At Herrenknecht headquarters in Schwanau and at the company's Swiss branch we are proud to have supplied essential technology for excavation of the Gotthard Base Tunnel, in the form of four TBMs.
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- Flying through the Swiss Alps
- On track: The Alps are key to transit traffic through Europe. Some 80% of freight transport between Italy and the other EU countries goes through the Alps. Until now, two thirds of that traffic has been by road, principally all along the Brenner Pass, Austria, the Fréjus and Mont Cenis Passes in France, and the Gotthard corridor in Switzerland. The European transport concept aims to transfer part of that road traffic onto the railways, in particular in Alpine regions. Switzerland's neighbours have bindingly agreed to provide high-speed rail corridors to serve as connections to the Gotthard.
- The New Alpine Transversal (NEAT) will make this high-speed traffic through the Alps possible. The rail route will provide an alternative to air travel, since the passenger trains will reach speeds of 200 to 250km/hr. The Zimmerberg Base Tunnel, the Gotthard Base Tunnel and the Ceneri Base Tunnel will reduce travelling times for passengers between Zurich and Milan from 4h 10 min to 2h 40 min. This will make a quick jaunt across the Alps for lunch possible.
- Road traffic through the Alps currently doubles in volume every eight years. Tailbacks of several kilometers have long become a daily occurrence at the Gotthard road tunnel. This is why freight transport is to be shifted to rail. The two NEAT axes at the Gotthard and Lötschberg mountains will more than double freight capacity from its current 20 million to around 50 million tonnes per year. They will not only allow more frequent rail traffic, the flat rail concept will also mean that trains can be considerably longer and twice as heavy (4,000 tonne instead of the current 2,000 tonne). This will make the helper locomotives, currently necessary on inclines, a thing of the past. The new highest point will be at the same altitude as the city of Bern, that is 550m above sea level. As a comparison, the highest point of the existing mountain railway is 1,150m above sea level. The route through Switzerland will thus become much flatter and 40km shorter. Freight trains will travel at speeds of up to 160km/hr – twice as fast as now.
- Tunnelling using drill+blast methods between the Faido and Sedrun intermediate headings was also an extremely technical challenge. Here, the tunnellers blasted huge underground stations out of the rock. They will serve as special stopping bays for trains in emergencies and allow trains to cross from one tack to the other as needed. A sophisticated system of transverse and connecting tunnels guarantees that smoke can escape and fresh air can enter the tunnel. The two ‘multifunctional stations' are huge construction sites in themselves. Here, the rock presented tunnellers with a particular drill+blast challenge.
- The mountain pressure in some sections was so high that the usual method of increasing the target dimensions of the excavating cross section was of no use. Normally, this gives the mountain the opportunity to 'let off steam' – the more it deforms, the more mountain pressure is released. But in the critical zones of the Gotthard Base Tunnel, stability could not be achieved by just permitting deformation. A counterforce was needed against the mountain to stop the cavity from reclosing completely. The solution was to use telescopically slidable rings. In this method, two telescopically slidable steel half-rings are connected to form full rings inside the tunnel cross section, excavated with an overcut of about 70cm. The ring segments slide slowly together under the mountain pressure until their ends meet and they stabilize each other.
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56m in just 24 hours
After a major overhaul, the two Herrenknecht gripper TBMs, Gabi 1 and 2, completed the northern Erstfeld-Amsteg section with a length of just over 7km in 2009.
- The geological conditions there were almost ideal. This meant a Gotthard tunnelling record could be set in late summer 2009. In the space of only 24 hours, Gabi 2 cut through 56m of the mountain – a world record for a TBM of this size. On June 16 and September 16, 2009, the construction site teams in the north reached their destinations in Amsteg after only 18 months, that is, six months ahead of schedule. This breakthrough was a prime example of the tunnel builders' and the machines' precision. Both TBMs had deviated from the ideal line, horizontally by 4mm and vertically by 8mm– millimeter precision in the truest sense.
- At this time, TBMs Sissi and Heidi were still working in the mountain in the south. Although Heidi had some problems with a rock collapse in the western tube between Faido and Sedrun in March 2010, the subsequent stabilization measures only interrupted tunnelling until July 2010. Luckily enough, this event had almost no impact whatsoever on the project schedule. Work continues, including that of the two tunnel lining units, supplied by the Herrenknecht branch company Maschinen- und Stahlbau Dresden, which follow the two TBM at a respectable distance. These 600m-long 'worms' lay drainage pipes, install sealing systems and concrete the vaults in 12m stages, preparing the tunnels, at 600m per month, for installation of the railway technology.
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High celebrations and congratulations at the final breakthrough of the first tube on 15 Oct, 2010
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October 15, 2010 - first main breakthrough
On Friday, October 15, 2010, breakthrough was achieved in the eastern tube. Breakthrough in the western tube is expected to take place in spring 2011. A few years of finishing work will then follow, to turn the tunnel into a functioning high-speed rail route. The work of the tunnel builders and the machines is now approaching its end. And the results are very satisfying. All risks were dealt with, all setbacks were overcome, all emotional rollercoaster rides were survived. And schedules were adhered to, despite the almost unimaginable complexity of the project. Time lost in one place was made up for elsewhere. On the occasion of the last stage goal, the Erstfeld – Amsteg breakthrough – Moritz Leuenberger, Member of the Swiss Federal Council, spoke of a "triumphant victory over the doubters and moaners". His motto was "no matter how high the mountain, no matter how hard the rock, where there's a will there's a way. We can do it, because we want it." - Martin Herrenknecht, Chairman of the Board of Management of Herrenknecht AG, also summed it up in his own words: "Anyone who masters such a huge project is at the pinnacle of infrastructure development. Europe will take off its hat to Switzerland as soon as the first trains start speeding through the new Gotthard Base Tunnel. The trust the Swiss have placed in Herrenknecht technology is the greatest complement we could ever receive as a company."
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Gotthard TBM safely across the Piora Mulda - TunnelTalk, Nov 2008
Great celebrations for Gotthard TBM arrival - TunnelTalk, July 2009
History in the making at St Gotthard - TunnelTalk, Oct 2010
Gotthard concrete lining - Maximising the advantage - TunnelTalk, December 2004
Concrete contribution to Gotthard undertaking - TunnelTalk, Oct 2010
Ceneri Base Tunnel start - TunnelTalk, Nov 2008
Gallery: Stills from live TV coverage of the breakthrough on Friday 15 Oct 2010
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