Lötschberg Base Tunnel
24 April 2008
Construction of the 34,6 Km Lötschberg base tunnel is well underway. BLS AlpTransit sub-contractor Grisoni-Zaugg is using a Wirtgen SP 500 slipform paver to construct the concrete trough for the slab track on a 7 km long single-track section between Mitholz and Frutigen. By the time construction is finished the SP 500 will have placed about 8000 m3 of concrete in extremely cramped conditions.
According to project manager Luc Giroud, “The 3,5 m wide concrete trough is paved without reinforcement; to an accuracy of ±10 mm. We can achieve a maximum output of 400 m per day, about 500 m3 of concrete.”
Concrete is dumped in front of the spreading plough. A narrow curing platform runs immediately behind the paver. Here, two of the paver crew put the finishing touches to the trough, including a broom for both tracks. A curing agent is then used to prevent premature shrinkage cracks. Additional joints are added every 4,8 m intervals, and drainage shafts every 40 m.