A masterpiece of engineering is the new Loetschberg base tunnel in Switzerland. The writer feels that he has some personal connection to this structure, as he did some mountaineering in the area during his student days and traveled
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the old tunnel. With a minimum of alpinistic knowledge, he and a friend clambered around in the Bernese Highlands some 50 years ago and, among others, took on the Balmhorn (3700 m), laboring up across endless snow fields and through thin air where each step became an excruciating effort all the while afraid of falling into a crevasse. Then, a day later, they crossed the Loetschen Pass (2690 m) where a thunderstorm caught up with them, and between lightning strikes flashing off rocks, they pulled their ice picks behind them in the vague hope of avoiding a hit. Now, some 2000 m down in the mountain, runs the base tunnel, some 400 m deeper in the mountain and somewhat west of the pass. The old Loetschberg tunnel, now called the mountain route, was opened for traffic in 1913. It was considered an engineering marvel of its time. The trains had to climb to a higher level to enter a tunnel about half the present length. This, however, unbeknownst to the engineers of the day, was high enough to cut into the gravel filled glacial trough of the Gastern valley. That led to a severe tunnel accident when a water-gravel mix burst into the tunnel under high pressure as soon as the tunnel pierced the glacial trough. The alignment had to be abandoned and instead of crossing the trough it had to continue deep enough in the mountain along the valley until it could safely cross it and then continue
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through the Loetschberg mountain. The base tunnel circumvents this area by staying west of it. From its north portal at Frutigen, at 777 m altitude, the new tunnel climbs to its crest at 828 m and descends to the south portal at Raron in the Rhone valley at 654 m, over a total length of 34.6 km. It consists of two single track tubes 40 m apart with some 70 m2 cross section each. In addition there is a service tunnel paralleling the main tunnel as a safety feature. There are cross connections between the parallel tubes every 333 m, two rescue exits, three venting stations, and several independent operation centers that are elements of the tunnel’s safety system. Only the southern part is presently double track, a main stretch is one track, and further expansion is scheduled to be undertaken according to demand.
The tunnel boring machine diameter was 9.43 m. Some 16 million tons of material were broken out. Dividing this mass by a rock density of about 3 t/m3 gives some 5 million m3, a cube 170 m long, wide, and high. A good part of this material is granite and granodiorite of the Aar massif and another major part is of the northern foreland formations. Some
of the material was recycled into concrete for tunnel linings and associated structures.
The old tunnel starts some 10 km further south and its portal is reached by two switchbacks between Frutigen and Kandersteg that consisted partly of major tunnels. From there it climbed to its crest at 1240 m. Also on the south side the old tunnel ended further up in the mountains at Goppenstein from where it ramped down into the Rhone valley to Brig where the Simplon tunnel takes off in direction Bellinzona. The old line will remain in operation. It is planned to be used by freight trains from south to north, as in this direction there are more empty cars. The heavy freight trains, usually north-south directed, will use the base tunnel.
The base tunnel was excavated from three points in addition to the two portals and the first phase was completed on schedule in eight years. The cost was about 2.6 billion Euros. Until December 2007 the tunnel is to be used only by heavy freight trains in the north south direction. Passenger trains are still going via the mountain route, but a test run with a German ICE-S train reached 280 km/h. All trains are pulled by electric locomotives and they are just swooshing along the welded and concrete embedded tracks. The high speed alpine traverse is expected to cut travel time between Bern and Milano by 1 h 8 min to a total of 2 h 55 min. Travel speed through the tunnel is expected to be 250 km/h (156 mph). The Swiss want to get the heavy trucks out of their towns and off their roads and mountain passes. Another even longer tunnel, the Gotthard base tunnel, with 57 km length is scheduled for completion in 2017 (VDI, Bern, 15/6/07, wop; www.ita-aites.org: The Loetschberg Base Tunnel – Lessons Learned by F. Vuilleumier and M. Aeschbach). WOW.