TUNNELLING IN OPALINUS CLAYSHALE IN SWITZERLAND

Numerous tunnels have been built and new tunnels are planned in the Swiss Jura Mountains, and most of them intersect Opalinus Clayshale. This presentation reviews several tunnel case histories which show that Opalinus Clayshale can be quite problematic by swelling during construction and also during operation if the invert cover is not strong enough and if water can penetrate into the shale. Modern testing methods and a newly developed behavioral model based on these test are then presented. They clearly show that Opalinus Clayshale when unloaded as it can occur around the tunnel perimeter swells which in turn can induce creep and even failure. Considering this behavior in design and construction will reduce swelling and creep.