Stability of Shallow Tunnel Using Rigid Blocks and Finite-Element Upper Bound Solutions

Abstract

Two methods of upper bound solutions were used to calculate the needed support pressure σT for shallow tunnel stability in cohesive-frictional ground. One uses a proposed rigid blocks failure mechanism for shallow rectangular tunnel of upper bound solution, and another uses a finite-element upper bound solution with linear program. In the rigid blocks failure mechanism, the velocity discontinuities in the side wall of the shallow rectangular tunnel occurred in both radial and tangent directions, so as to increase its flexibility. The main formulas for calculating support pressure σT were deduced for the above two methods; thereafter, the corresponding calculating programs were compiled. The needed support pressure σT for shallow tunnel stability and its parametric influences were obtained. The results show that both methods can be used effectively to analyze the stability problems of shallow rectangular tunnel using upper bound solutions.