There is no doubt finally that the giant AlpTransit project is under way. On both north-south axes through the high Alps access tunnels are being completed, start chambers hollowed out and portals begun. Work camps have appeared in the narrow mountain valleys and at high points for intermediate attacks. TBMs have been ordered and are under assembly or on several smaller adits, already at work.
Financing for the scheme was released by one of Switzerland’s referendum votes in November 1998, when a SFr30bn ($17bn) road and petrol tax scheme was agreed to raise money for transport infrastructure. About SFr14bn goes to the first phase of the scheme, and the much larger share to the Gotthard.
Despite some variations and phasing of sections, the project is the same as envisaged in the mid-1990s (T&TI November 1996).
Two routes will be created through the massive mountains block of the Alps. The smaller, at Lötschberg on the western side of the country, will link France and West Germany through Basel and the capital Bern down to the Rhone valley and on to Milan, taking advantage of the existing Simplon Tunnel for the last section of the route.
The other scheme runs up to 2,000m deep beneath the famous high Gotthard pass, linking central and eastern Germany, through Zurich and again on to the Italian high-hub at Milan. Gotthard will use TGV-type trains and tilting trains, the Lötschberg tilting trains and more conventional fast stock. Both will also carry freight.
Lötschberg
For the Lötschberg project the main works comprise essentially a single main link cutting beneath the existing Lötschberg high tunnel, built early in the century with a line running from Thun to Brig.
Two 34.6km-long single track tunnels will be built; as with Gotthard, a basic fire and safety principle is the use of the opposite tunnel as an emergency evacuation system in the event of disaster.
There are connecting tunnels every 325m and, in the central section, the running tunnels will also feature a complex of side tunnels and smaller vent and ventilation bores, designed to carry away heat and smoke in a disaster.
Because of these safety needs both main drives will be completed in time for the intended 2006 running date, even though a 14km length of the western tunnel will remain without rails or signals. Northbound trains will use a crossover at the Ferden mid-point to switch into single-track operation.
Peter Teuscher, client BLS AlpTransit‘s project director, explains: “The reason is, of course, financing.” He hopes that the second stage can go ahead quite rapidly, and equally, that a western branch connection at the southern end, now being used as an access drive, will also be fitted out.
Despite the phasing of the project it is still too big for a single drive. “It took 10 years to complete the high tunnel, and even with modern technology we would need too long without intermediate attacks,” says Teuscher.
Lötschberg is split into four main contracts, therefore, as well as several other laregscale preparation works. The first to be awarded in February this year was the more northern Mitholz section, which involves two 8.7km drives southwards, and one 7.4km north. The SFr533M Satco Mitholz joint venture brought together Swiss firms Rothpletz, Lienhard and Walo Bertschinger with France’s Dumez, Austria’s Ilbau and Sweden’s Skanska International.
AlpTransit has specified drill and blast for this section which runs through the lower northern mountains. Geology on Lötschberg is not exceptionally difficult, but could cause some problems as it contains folded sedimentary rocks of flysch, nappe and some sandstone. Water inflow could be troublesome too, though a special test tunnel built in the mid-90s showed less than expected.
TBM work was considered too risky. Progress is “on schedule so far”, says Teuscher, and tunnels are achieving about 20m a day.
The test tunnel will serve as the safety tunnel for the northernmost section of the route, and this is the reason only one northbound drive is needed now. The work is heading out of a “footprint” of caverns and links created in a smaller contract by joint venture Frutiger, Batigroup and Seeburger & Jord. The same group made the 1,700m-long “window tunnel”, which gives access to the start point from an external work camp perched half-way up the steep valley climb from Frutiger to the Lötschberg Pass.
A longer, 4.2km window tunnel is nearing completion on the south side of the mountains to hit a start point around 12km in from the southern portal. This will be for the Ferden contract, as yet unawarded, for deep, twin-drives 6.6km north and 1.5km south.
The work is in the granite Aar massive and expected to be in relatively good ground, although the depth brings special problems, such as high ground heat. Rock temperatures in the mid 30°C will compound the heat accumulation from TBM motors, which means that extensive cooling and ventilation will be needed.
Two more contracts start from the flat valley bottom of the Rhone river, the smaller for a 3.1km spur tunnel from Steg and a 5.3km part of the main drive north. Another 2.5km section south is also included. The spur is the same 9.4m diameter drive as the main tunnels, and should eventually become a running tunnel.
MaTrans, a consortium of Switzerland’s Marti Tunnelbau, Germany’s Waltergruppe, Austria’s Porr and the UK’s Balfour Beatty has this work. It also recently won the contract for the main drives from the southern portal at Raron. Both contracts together are worth about $500M.
The Steg TBM is under assembly and others are ordered.
Gotthard
The Gotthard project is much bigger than Lötschberg, and will certainly be much more difficult, as it is deeper and hotter to tunnel in. And it will open for service much later, about 2011, rather than 2006.
Initial plans and eventually, it is hoped, the full scheme, include five main tunnels and stretches of new high-speed line running virtually from Zurich to the southern section of Switzerland just north of Lugano, a route approaching 100km.
A tunnel for Mt. Ceneri in the south is about 15km long, another out of Zurich more than 12km. There are some shorter tunnels, but all of them will come later, as will some sections of open air high-speed line between tunnels.
But the largest element of the plan, and the one forming the core of the first phase, is a deep tunnel beneath the Gotthard pass. At 57km long, it will be a world record holder.
Twin tubes will carry high-speed trains and freight from a portal at Erstfeld near Lake Lucerne in the north all the way to Bodio in the south. Cross galleries will link the tunnels all along the length to provide emergency escape routes.
Although the northern section runs through some of the same rock as the Lötschberg, namely the Aar massif, the big tunnel also runs through much more troubled ground. The Aar is formed of granites and gneiss and is suitable for TBMs, as is the central Gotthard massif with even harder granites. To the south there is a long section of Pennine gneiss, which is also good for TBM work. At least eight big machines will be running during the main works.
Drives will not be easy, especially at depths of up to 2200m, where rock temperatures could rise to 45°C and pressures will make rock burst a likelihood at any time. Special cooling systems will have to be used for the TBMs as they spill out even more heat.
But in between these blocks are much more difficult sections. At first it was feared the most troublesome of all would be so-called Piora Mulda, a band of soft, friable stone that, in the presence of water, turns to what Swiss tunnellers describe as a kind of sugar. A mere 300m layer could hold up work for months, it was thought.
Just how soft it is was demonstrated graphically during cnstruction of a test tunnel five years ago. Drills hit the rock and a flood of water and white sandy material flowed in around the trucks inside. It was still being dug out two months later.
The tests proved positive. Inclined bores from the cleaned-up test tunnel to rail tunnel level 300m below showed the Piora at the lower level to be dry and anhydrite, in which state it can be tunnelled. Plans to use the test tunnel to make a gallery for substantial grouting and stabilisation work were abandoned, along with the tunnel.
But the Tavetsch intermediate massif 20km from the other end of the Gotthard is not so amenable to good fortune. Here some 4km of sometimes fairly soft sedimentary rock has been ground around between two granite massifs for millions of years. The rock is heavily fractured and at places little more than pebbles, at best riven with faults. It is likely to carry water and flows could be substantial from a surface up to 2,000m above.
Getting through this section will require special measures and careful hand tunnelling, using drill and blast and other methods. Client AlpTransit Gotthard AG, a different privatised company to the Lötschberg client, says that this sector is critical for the tunnel’s construction. The effort to get through its 6.7km will take longer than most of the main tunnel drives. “It will be the most expansive section, too,” says Jakob Blickenstorfer, AlpTransit engineer based at Sedrun.
Extreme squeezing ground is one problem expected and a telescopic steel support arch has been borrowed from German mine technology to yield in tunnel diameters that must be as much as 4m over-bored to achieve the final 9.5m diameter, or 9m after lining. Arches have a 1.5m “give” in them.
Arches may need spacing down to 033m intervals in places. Some sections will need vast amount of anchors too, up to 400m length for a 1m length of tunnel.
“The squeezing does eventually stop,” says Mr Blickenstorfer.
As at Lötschberg, Gotthard’s construction will use several attack points, starting inside the mountains from adits. One of these is under construction at Amsteg 7km from the northern end of the tunnel another at Faido near the southern end. A tunnel around a rock debris slide is under construction at the southern portal to allow work on the main drive to begin in the good rock behind it.
These works have all started recently. But for the Tavetsch area an access has been under way for over three years, the Sedrun tunnel and shaft. From a 1km tunnel into the mountain from Sedrun valley, there now plunges an 840m deep shaft, now being widened at the base into a working chamber. The shaft will eventually form part of emergency escape facilities.
These works, all “temporary”, demonstrate the scale of the project, since they are all big projects. None of the big project awards has yet been made and international consortia are jostling for position. Drives are due from Erstfeld south, from Amsteg, from Sedrun, Faido and from the southern portal.
One final problem remains. Planning permissions for the 7km stretch of Gotthard in the north from Erstfeld are still outstanding. This section has been most controversial politically, and local Canton authorities and city councils want the route to be changed. They want it extended to run as tunnel through a mountain to one side of the valley, rather than across the valley floor.
This section is critical for the final fitting out of the tunnel since it will be the route in for track and signalling equipment. The delay could yet affect the whole of the enormous project.
Related Files
Geological formations
Switzerland
