Mechanical behaviour of geo-encased sand columns: small scale experimental tests and numerical modelling

This paper presents experimental monotonic and cyclic test results on small scale sand columns reinforced by means of geosynthetics. The influence of the stiffness of the georeinforcement on the system mechanical response is discussed as well as that of the previous loading history. The experimental test results have also been numerically simulated by employing a 3D finite difference commercial code. A parametric study concerning the georeinforcement stiffness and the soil-column interface friction angle is presented. The results prove the influence of the encasing geosynthetic on the overall stiffness of the system, as well as of the stiffening effect induced by a possible preload applied on the column. The effect of shear stresses at column-soil interface is also observed to play a non negligible role, which is expected to become even more evident for real scale geo-encased columns. Numerical approaches based on standard constitutive models are able to capture the behaviour of the system under virgin load, but they totally fail in reproducing the unload-reloading response.