On Rate-Dependency of Gothenburg Clay

On Rate-Dependency of Gothenburg Clay MATS OLSSON Department of Civil and Environmental Engineering Division of GeoEngineering Chalmers University of Technology ABSTRACT Long-term settlements in clay constitute a major engineering challenge in areas with deep deposits of soft clay. This dissertation aims to extend the understanding and theoretical framework of rate-dependent soil behaviour, so that uncertainties in predictions of long-term settlements are significantly reduced. This is first done by looking at the basic behaviour of soft soils and some existing advanced constitutive models. The research comprised of the development of a new rate-dependent model called MAC-s which was implemented in COMSOL Multiphysics. A focus of the latter development was the prediction of the coefficient of lateral earth pressure at rest, K0, during creep and unloading. In order to help validate the K0 value, i.e. the ratio between the horizontal and vertical effective stress at normal consolidated conditions, a novel K0-triaxial cell was developed and tested on samples of soft Gothenburg clay. The simulations of oedometer and undrained triaxial tests with the new model are in good agreement with experimental data. The test results from the K0-triaxial cell indicate that the normally consolidated K0 value of soft Gothenburg clay is in the range of 0.50-0.55, which does not match the commonly used empirical relations, based on the index properties of the clay. More experimental tests should be performed to validate the model formulation, and gather comprehensive data on K0 values for soft soils