Failure of support measures – analysis based on 3 examples

Abstract Failure scenarios involving tunnel collapse usually occur due to unexpected faults at the face because the support was not designed for this or was underestimated. Failure of the support behind the working face occurs less frequently and can have various causes. Three examples are used to show which stress redistribution mechanisms can lead to failure of the rock support. Using the example of the Arlberg road tunnel, the failure during bench excavation showed that fracture processes exaggerate and due to developing of extended fracture planes trigger a failure of the support. The transfer of high rock stresses to deeper areas prevented the collapse of the cavity in accordance with what Kastner called the protection zone. The example of the Landrückentunnel showed that the excavation of the bench including a heading invert arch with a distance of just 6 m to the ring closure can trigger a total failure of the tunnel. The example of the cavern of the crossover at the Channel Tunnel showed which influences, such as redistribution of the pore water pressure and the longitudinal load‐bearing effect of the support, can result in an overloading of the shotcrete structure.