Pseudo-static analysis of tunnel face stability using the Mohr-Coulomb strength criterion

Abstract

The paper addresses the stability analysis of a circular tunnel face driven by a pressurized shield by means of the limit analysis kinematic approach implemented in the context of the Mohr-Coulomb strength condition. Emphasis is given to the assessment of the effects of seismic loading on the value of face support pressure that is required to prevent failure. The approach relies upon the pseudo-static method to model the destabilizing effects induced by the inertial forces associated with the passage of seismic waves in the ground. Rigorous limit analysis solutions for the limit face supporting pressure are derived from the analytical implementation of 3D and 2D failure mechanisms specifically devised for dealing with such a stability analysis problem. Indeed, original analytical expressions are provided and allow the evaluation of the pressure stabilizing the tunnel face. The accuracy of the approach predictions is assessed by comparison with available experimental and analytical results as well as with 2D finite element solutions. The influence of some relevant problem parameters in the context of tunnel face stability analysis is finally investigated, thus providing some preliminary guidelines for practical use in tunnel engineering.