Introduction

Potts et al. (1997) used a finite element analysis to explore a link between strain softening and delayed failures of old railway slopes cut into stiff plastic clays. Strain softening causes a soil’s strength to reduce from a peak to residual state. The strength loss does not occur simultaneously along a potential rupture zone because the rate of softening is linked with the magnitude of shear straining. As a result, the failure is progressive in the sense that the rupture surface propagates through the soil profile over time.

SIGMA/W’s coupled formulation, in combination with the Mohr-Coulomb Hardening/Softening, was used to simulate this case history and therefore to explore the progressive failure mechanism.