SHALLOW FOUNDATIONS ON GRANULAR SOILS REINFORCED BY MEANS OF GEO-SYNTHETICS

The use of synthetic reinforcements to increase the bearing capacity of shallow foundations is still limited. In fact there is some criticism about it, also because the comprehension of the mechanical effects, induced by the presence of geo-synthetic layers within the soil, is not yet satisfactory. In this paper, the mechanical response of scale model strip shallow foundations on geo-grid-reinforced sand is experimentally analysed. The load is centred and vertically applied. Foundations are tested under vertical displacement control; as a consequence, the post-peak regime is analysed, too. The geo-synthetic layer number, the material which the reinforcement consists of and the depth at which reinforcements are placed, are the parameters taken into account. The role played by them on footing settlements, on bearing capacity and on the ductility of the mechanical response is analysed. It will be shown that the presence of synthetic reinforcements dramatically increases the foundation bearing capacity and makes the mechanical response more ductile: in some cases softening regime disappears, too. On the contrary, the initial stiffness of the system does not seem to be influenced at all. A basic mechanical interpretation of the experimental results based on the kinematic limit analysis is introduced. Particular attention is paid to describe the dependence of failure mechanism shapes on all the parameters mentioned above.