MOTION SIMULATION OF RAPID LONG RUN-OUT LOESS LANDSLIDE AT DONGFENG IN JINGYANG, SHAANXI

Abstract

The Dongfeng loess landslide on the south platform in Jing Yang is a typical type of high-speed long distant landslides, induced by the long-term irrigation at the top tableland of the slope. After field investigation, loess samples are taken in different parts of the slope. The intact samples taken in the central slope(Q2) are utilized to do the CU tests, and the ones taken in the slope bottom(Q1) are saturated and then used to conduct the CU tests. Results show that both the unsaturated loess Q2 and the saturated loess Q1 display significantly stress decrease. However, they have different reasons. For the former is caused by the decline of structure strength, while the latter is caused by the pore water pressure generated during the shearing process. All above reveal that once the slope failure occurs, there will be high initiating speed. The ring shear tests are conducted on the sand on the first terrace out of the slope toe to obtain the effective residual friction angle. Then according to the situation of water contents, pore pressure coefficients in different parts are obtained. Then the landslide movement process can be simulated by Sassas landslide motion model,which can show the speed changes and the coverage of landslide. The simulation results are in good agreement with the measures results. The highest speed can reach 37m s-1,also revealing that it is a high speed landslide. The loess landslide with high initial velocity down to the slope foot in the saturate sand layer of the first terraces and liquefaction in the sand layer is the main factor of its remote movement.