<p>The squeezing of tunnels is a common phenomenon in poor rock masses under high in situ stress conditions. The critical strain parameter is an indicator that allows the degree of squeezing potential to be quantified. It is defined as the strain level on ...

In tunnelling through heterogeneous rock masses, such as the flysch, it is important to attempt to obtain reliable estimates of potential tunnelling problems as early as possible. This enables the tunnel designer to focus on the selection of optimum routes ...