Cave-ins in the Paijanne Tunnel and their repair

Two cave-ins occurred in the Paijanne Tunnel, the repair of both being comp leted in the spring of 1999. One cave-in occurred near Hameenkoski and the other near Pulkkila. The Hameenkoski cave-in was probably caused by the acc elerated weathering of a weakness zone, which led to a. rather complex cave -in process. The construction of the funnel in the 1970s changed the ground water conditions, thus increasing the rate of weathering. The Hameenkoski c ave-in was repaired by a bypass tunnel. The Pulkkila cave-in was caused by a water flow, which flushed out joint fillings, leading to the fall of key- blocks. The Pulkkila cave-in was repaired by penetrating the cave-in. (C) 2 000 Published by Elsevier Science Ltd. All rights reserved.