Undrained Stability of Tunnel with a Longitudinal Gradient

This paper involves the effects of longitudinal gradient into the stability analyses of tunnel face in undrained clay. A kinematical approach of limit analysis based on continuous velocity field is employed to estimate the upper-bound solution of supporting pressure on tunnel face. The obtained results demonstrate significant influences of the longitudinal gradient on the stability of tunnel face below an inclined ground surface. When tunnels are excavated below a horizontal ground surface, the influences are minor and then can be ignored in practice.