A two-phase model and related numerical tool for the design of soil structures reinforced by stiff linear inclusions

A two-phase macroscopic model is presented for ascertaining the overall linear elastic behaviour of a soil reinforced by stiff long inclusions, with a particular emphasis on the shear and flexural behaviour of the reinforcements. Based on a minimum principle for the potential energy of any two-phase system, expressed as a function of the kinematically admissible displacement and rotation fields, a finite element formulation is established, resulting in the elaboration of a numerical computer code devoted to the simulation of any reinforced soil structure under plane strain conditions. This finite element code is applied to the evaluation of the settlements experienced by a rigid raft foundation placed on top of a soil reinforced by a group of vertical piles, and subject to combined loading conditions. One of the important conclusions which may be drawn from such a quantitative analysis is that the shear and flexural behaviour of the reinforcing piles, as well as the way these piles are connected to the foundation, play a decisive role in the case of lateral loading.