The constitutive modelling of London Clay

Abstract

Advances in understanding real soil behaviour, achieved over the past twenty years, and subsequent developments of relevant soil constitutive models, have greatly enhanced the predictive ability of numerical analyses of geotechnical structures. Of particular relevance, especially for serviceability limit state (SLS) design, has been the understanding of soils' small strain behaviour. For the behaviour of London Clay, initially developed models were simple curve-fitting techniques that reproduce stiffness dependence on stress and strain level, which has shown some successes in predicting SLS behaviours. Modelling failure of London Clay is significantly more complex due to its overconsolidated and fissured nature. More recent developments in soil constitutive modelling have therefore tried to encompass most important aspects of clay behaviour within the unified framework of critical state. However, even these advanced models have insufficient features to simulate the behaviour of overconsolidated clays. In this paper, a study has been made, comparing high quality laboratory triaxial data on London Clay with the predictions of two constitutive models, highlighting these deficiencies. It is shown how relatively simple modifications of advanced models, to capture the anisotropy of small strain stiffness and to impose a strength curtailment to represent strain localisation, can significantly improve the predictions of laboratory experiments.