Stability of accumulation landslides with broken-line slip surface under action of continuous rainfall

The occurrence of accumulation landslides on the edge of the Qinghai-Tibet Plateau is closely related to rainfall, and many of the landslides are those with broken-line slip surface. In order to explore the stability of the accumulation slope with broken-line slip surface under the continuous rainfall, firstly, based on the traditional rainfall infiltration Green-Ampt (GA) model, considering the influences of the slope angle, seepage in saturated zone and seepage coefficient in unsaturated zone, a rainfall infiltration model suitable for finite-length slopes is established. Secondly, combining the unbalanced thrust method and the rainfall infiltration model, the formula for calculating the stability of the accumulation slope with broken-line slip surface under the continuous rainfall is derived. Finally, the results of field infiltration tests are compared to verify the rationality of the proposed infiltration model and with those of the traditional stability algorithm based on the Jiangdingya accumulation landslide of Zhouqu county. The results shows that: (1) The rainfall intensity, slope angle and permeability coefficient all affect the formation speed of the saturated layer of the slope and the spreading speed of the thickness of wetting layer. (2) At the beginning of rainfall infiltration, the three models obtained the same wetting layer expansion rate. With the continuous rainfall, the wetting layer expansion rate calculated by the model provided in this paper was higher than that of the G-A model but lower than that of the infiltration model with assumption of stratification. (3) The stability of the Jiangdingya accumulation landslide gradually decreases with the continuous rainfall. At the beginning of the rainfall, the stability of the landslide decreases rapidly. At the later stage of rainfall, the rate of stability decline gradually slows down. The slope sliding time obtained by the proposed stability method is earlier than that by the traditional infiltration model. The research results can be used as a reference for the stability analysis of accumulation slopes under the continuous rainfall.