Some Factors Affecting the Predictions of Ground Movements Around an Excavation in Stiff Clay

Abstract

The paper describes a sensitivity study of predictions of excavation behaviour in a heavily overconsolidated clay using a non-linear cross-anisotropic elastic model for the soil. The model is experimentally based and is capable of including non-linearity of stress-strain behaviour, dependence of stiffness on both stress level and stress path direction, and changes in stiffness caused by changes in the stress path direction. Analyses are reported of an instrumented full-scale trial excavation and computed displacements are compared with the observed behaviour. Firstly, the effect of including anisotropy is quantified, by comparing analyses with isotropic and anisotropic soil models. The effects of modelling the recent stress history and changes in the stress path direction during excavation are then investigated. Finally, analyses with linear and non-linear stress-strain behaviour are compared to isolate the effect of including a strain-dependent stiffness.