Evaluation of the lateral earth pressure in unsaturated soils with finite element limit analysis using second-order cone programming

This paper aims at studying the active and passive earth pressures on the retaining structures having an unsaturated backfill. To this end, the well-established lower bound limit analysis coupled with the finite element method and the second-order cone programming (SOCP) has been employed to generate the admissible stress field within the soil medium behind the retaining wall. In order to simulate the unsaturated soil condition, the unified effective stress approach is adopted and implemented in the universal Mohr-Coulomb yield criterion. Using the results of several numerical simulations, the influence of various controlling parameters, including flow rate condition, soil–water retention curve (SWRC) and groundwater table level on the response of the retaining wall with an unsaturated backfill is thoroughly examined. Furthermore, the active and passive earth pressures are rigorously evaluated accounting for the variations of the wall height, soil type, effective internal friction angle, soil-wall roughness and soil inherent anisotropy. It is shown that as the existence of suction stress in unsaturated soils results in the greater values of the effective stress, and consequently the soil shear strength, it would lead to the lower active and higher passive lateral pressures exerted on the retaining structure.