Rigid pile improvement under vertical cyclic loading: 1g laboratory small-scale modelling

Abstract

The research work presented in this paper is a contribution to the understanding of the behaviour of soil reinforcement by rigid inclusions under a quasi-static vertical cyclic loading. While the system behaviour under static loading is well known, the response of this technique under cyclic and/or dynamic loading is not yet fully understood and cannot be predicted. The first step of the study consists in performing a series of tests on a small-scale laboratory model, with a scale factor of 1/10 on the lengths, simulating the case of rigid inclusions using different thicknesses of the load transfer platform (LTP) considering different boundary conditions at the ground surface. A Digital Image Correlation (DIC) method is also used in order to study the displacement field inside the LTP. The parametric study performed with the physical model gives an insight on the influence of LTP's thickness and on the presence of a rigid slab at its surface on the behaviour of this technique under cyclic loading. The experimental results highlighted an accumulation of the settlements during the cyclic loading in all the studied cases. They also showed that the use of a small LTP thickness decreases the settlements’ accumulation observed during the cycles. Results also showed that the presence of the rigid slab increases the settlements’ accumulation. Nonetheless, its presence results in a reduction of the total settlement during a further monotonic loading. In a second step, the experimental results will serve as a database for the validation of a 3D numerical model.