Centrifuge modelling of rainfall-induced slope failure in silty soils and validation of intensity-duration curves

As the southeastern coastal area in China has a humid climate,lots of landslides in soil slopes are induced by rainfall during the rainy season and typhoons every year. It is of great importance to investigate the failure modes and mechanism of rainfall-induced slope instability. A rainfall simulator installed on the centrifuge model box is developed, and the failure process of the silty slope subjected to different rainfall intensities is reproduced. The observed failure mode startes from local failure at the slope toe, extends upward and finishes with a global shallow landslide. The depth of the slip surface is 1 to 3 m. It is found that the data points of relationship between rainfall intensity and rainfall duration from the three centrifugal model tests are close to the intensity-duration curve proposed by Li et al. (2012) for the early warning of landslides in a residual soil slope in the southeastern coastal area of China. The back analyses of the experimental results indicate that unsaturated seepage analysis is able to simulate the rainfall infiltration processes into the slope, but it is difficult for the existing limit equilibrium methods to capture the local to global failure process induced by rainfall accurately. Based on the observed failure modes, the mitigation measures for this kind of rainfall-induced instability mainly include draining and retaining at the toe of slopes as well as reducing infiltration on the slope surface.