Unsaturated soil interacting with a rotating model wall

A new testing facility and set of procedures for performing retaining wall model tests in unsaturated soils are described. The facility enables a model wall to be rotated into or away from a soil sample about one of a number of rotation centres. The results of a single test in a decomposed granite sample are presented. The test sample was prepared using a modified moist tamping method involving a hand-held electric percussion compaction hammer. The compaction energy applied to each of ten thin layers of soil in forming the sample was controlled and enabled a uniform density to be achieved. Suction changes were measured using vibrating wire piezometers. Pressures on the wall were measured by earth pressure cells embedded in the wall face. Integrating the earth pressure profile enabled an equivalent load acting on the wall to be calculated, and was in reasonable agreement with the measured applied load. Soil deformations were recorded using photographic image velocimetry. The pattern of soil deformation observed, particularly strain localisations, was similar to those in tests on dry sands. The suction increases measured during the test were consistent with the volumetric dilation that occurred in the sample.