A numerical study of delayed failure of excavations

The finite element method is applied to an idealized, 20 m deep excavation in clayey soil. This excavation is stable just after the removal of mass, but develops failure before the stationary longterm condition is reached. The processes governing the time-dependent behaviour of the excavation and the occurrence of delayed failure are studied, as well as the effect of the dilatancy properties of the soil. The behaviour of the slope over time is studied with respect to pore pressures, stresses, deformations and shear mobilization. The effect of the dilatancy properties of the soil is examined by comparing dilative and contractive soil behaviour with the behaviour of a dilatancy neutral soil.