Work on 35km long Lötschberg Base Tunnel in Switzerland is proceeding rapidly towards the operational phase in 2007 with several adaptable travelling tunnel formwork units from Doka being used on hire for some of the trickier lining sections.
Contractor, the Swiss Alp Transit Consortium (SATCO), is using steel formwork for the routine sections of tunnel, but in less standard areas such as four ventilation tunnels and a funnel shaped section that broadens over a length of 275m, the standard set-up is only used to form the sidewalls. For the arched crowns, Doka formwork was chosen to complement the wall arrangement as “all components can be rented, are highly adaptable and are quick and easy to operate”.
The 275m long funnel section varies from 18.1m to 7.6m in width and from 9.95m to 7.95m in height. By using a heavy duty specification, the span was able to be kept open for vehicular access during operations. Adjustments to the section are carried out by means of hydraulic rams. After initial installation, the crew was soon able to achieve a one day casting cycle.
Two Doka travelling formwork units were used to line the four ventilation tunnels, a cylindrical unit and a conical unit. This approach accommodated the profiles required for the tunnels that are made up of a cylindrical middle section with conical ends.
As the majority of the bespoke forming operations were nearing completion, contractors’ supervisor, Philipp Häfliger said: “Using the travelling tunnel formwork units from Doka, we have been able to overcome every difficulty so far. They are really easy to adapt to the tunnel cross section and we are right on schedule.”
