Soft soil improvement by rigid inclusions under vertical cyclic loading: numerical back analysis

While the behaviour of rigid inclusion improvement systems under monotonic loading is well known, the response under cyclic loading is not yet fully understood and cannot be predicted due to the lack of knowledge about the load transfer mechanisms in the granular platform. This article proposes a three-dimensional numerical modelling under a quasi-static vertical cyclic loading. Numerical results are compared to experimental results obtained on a three-dimensional small scale model, to discuss the numerical procedure and the constitutive models implemented. For the load transfer platform, a shear hardening elastoplastic model is implemented; for the soft soil, the modified Cam Clay model is used, as it features well the compressive and swelling behaviour. Some aspects of the behaviour of the system could be correctly reproduced, such as the loads on inclusions and the settlements under monotonic loading, the settlement accumulation and the decrease of the load transfer onto the inclusions along the cyclic loading, as well as the qualitative influence of a rigid slab placed at the platform surface on the settlement accumulation. However, other features could not be satisfactorily taken into account, namely the behaviour under a rigid slab submitted to cyclic loading in terms of load on the inclusions.