Interaction of unsaturated sand with a retaining wall under various active movements

Estimation of the active earth pressure is a fundamental factor in the design of many geotechnical engineering structures. In the current study, in order to investigate the earth pressure in an active state, the results of fourteen retaining wall models in unsaturated and dry conditions are reported. The conducted models consisted of rigid retaining walls that were capable of translating, rotating about the toe, and rotating about the top. It is observed that the distribution of the earth pressure behind the model wall was nonlinear, and the nonlinearity rose by increasing suction in the soil. Results of image processing obtained from top and side views of the models besides the recorded earth pressures showed that the volume of the failure wedge behind the wall, and consequently the imposed force to the wall in active condition significantly decreased by slightly increasing the matric suction in sand. An equation that agrees well with experiments is presented to estimate the load that backfill imposed on the wall in similar soils.