The Sliding Failure Mechanisms of Granular Soil Slopes

In order to understand the slope failure mechanism of slopes due to rainfall infiltration, physical models of slopes composed of sand and silt were used to perform tests. Two kinds of model tests carried out in this study were: (1) sliding of dry sand slope, (2) slope failure due to rainfall infiltration. The particle image velocimetry (PIV) and the impact measurement device were utilized to investigate the impact force and the influencial area of the sliding of dry sand slopes. Different geological situations, fines content of slope and rainfall intensity were taken into consideration to understand the slope failure due to rainfall infiltration. Water was permeated into the slope from the top. The pore water pressure, the water content and the deposition of soil mass were measured. Test results show that failure of pure sand slopes was a sliding type. Water flow caused piping at the toe of the slope, and then retrogressed upward along the slope. The water content within slope increased suddenly when the sliding occurred. The flow type, failure occurred for slopes with 10% silt content, In addition, an erosion hole was observed on the upper slope near the crest. The failure mass contained a lot of water. Therefore, its mobility was better, flow velocity was fast, and the deposition area was wider than those of pure sand slopes.