Investigation of plastic zones around circular tunnels in strain-softening rock mass

This paper introduces a new numerical approach to model the strain-softening behaviour of the rock mass. The strain-softening process is simplified as a series of brittle-plastic ones and solving a strain-softening problem becomes finding a series of brittle-plastic solutions in the proposed numerical procedure. Moreover, the cohesive and frictional strength components can be mobilized separately as functions of plastic strain. Thereby, the cohesion weakening and frictional strengthening process can be captured for geomaterials. Numerical examples are presented and the results compared with those published, and it is shown that good agreement is obtained. Different strain-softening processes including different softening rates and modes of strength components' mobilization are investigated, and plastic zones around the tunnel in strain-softening rock mass are presented and the appropriateness of the parameters are discussed.