Undrained Stability Analysis of a Plane Strain Circular Tunnel Using Streamline Velocity Fields

Abstract

A new failure mechanism established from a streamline velocity field with energy dissipation through an internal deformable zone and the velocity discontinuity at its boundary is proposed. The application of the developed velocity field to the upper-bound theorem stability analysis of a shallow circular tunnel in nonhomogeneous undrained clay with a linear strength gradient of depth is further demonstrated. Comparisons of stability upper-bounds are made among the current mechanism with other reported solutions to verify the present method. A discussion on the optimal failure mechanism and the corresponding velocity field is presented.