Factors affecting rainfall-induced flowslides in laboratory flume tests

Using a small flume, a series of tests has been conducted to cause rainfall-induced flowslides. Based on monitoring of sliding distance and pore pressures, the process of pore-pressure generation in relation to sliding distance is examined. A set of test results on the temporal and longitudinal variation of sliding velocity is presented. By changing the initial dry density and sample thickness in tests on a silica sand, the effects of these two factors on the pore pressure build-up after failure and flowslide motion have been analysed. The test results showed that there was an optimal density for pore pressure build-up, at which both the moving velocity and run-out distance were greatest, and this optimal density was dependent on sample thickness. Additionally, a series of tests on mixtures of silica sand with different loess contents has been carried out to investigate the effects of fine-particle content on the flowslide motion, in which different modes of flowslide motion were observed; these probably were affected by the different rates of pore-pressure dissipation in the shear zone.