STABILITY OF SHALLOW TUNNELS IN SOFT GROUND

This paper examines the undrained stability of a shallow circular tunnel in soft ground using theoretical and experimental methods. Rigorous bounds on the loads required to resist collapse are derived using two numerical methods which are based on finite element formulations of the classical limit theorems. Both of these methods can account for the variation of shear strength with depth and lead to large linear programming problems. To improve the quality of the numerical solutions, the upper bounds from the finite element procedure are compared with those obtained from a number of rigid block mechanisms. The theoretical predictions, which are presented in the form of dimensionless stability charts, are compared against the results from controlled centrifuge experiments and their limitations are discussed. (A) For the covering abstract see IRRD 859983.