Interaction of a rotating rigid retaining wall with an unsaturated soil in experiments

The results of six retaining wall model tests are reported. The model tests consisted of a rigid retaining wall rotating about its toe into unsaturated and dry silty sand samples. For a given moisture content, the net earth pressures normal to the wall were largest in the densest samples. For a given density, the net earth pressures were largest in the samples with the largest suctions. As suction increased so did the soil stiffness, causing rupture surfaces to form and earth pressures to mobilise more rapidly as wall rotation progressed. However, similar rupture surface patterns eventually formed at large rotations whatever the initial suction. The earth pressure profiles and local mobilised earth pressure coefficients at large wall rotations, when interpreted using the effective stress concept, depended on sample density and were independent of suction. Simple functions defining the earth pressure profiles at large rotations are given and may be used to aid retaining wall design in similar soils.