RESEARCH ON RIVER-BLOCKING MECHANISM OF XIAOJIAQIAO LANDSLIDE AND DISASTERS OF CHAIN EFFECTS

Earthquake is considered to be one of the main factors of the generation of a landslide. Especially in high mountain gorge areas,the huge landslide body inrushes into the river and barriers the river,which may further expand the disaster areas and form a disaster chain. Taking Xiaojiaoqiao landslide for example,the three-dimensional(3D) instability process of the landslide is reconstructed by using dynamic finite element method based on detailed geologic investigation results of the landslide area. With the analytical results,the forming process and river-blocking mechanism of Xiaojiaqiao landslide can be divided into four phases:(1) earthquake triggering and progressive failure of the rock mass;(2) landslide body failure and sliding with high speed;(3) impacting the opposite slope,being disintegrated,and blocking the river and forming the landslide dam;and (4) density under the impacting. Based on the geological structure characteristics of the landslide dam and the stability analytical results under different cases,the stability of the slope of landslide dam is good under natural state,but there may induce local collapses with strong earthquake;and the most possible failure model may be the gradual erosion damage of topping. As for the internal rock structure with general stability,there is little possibility forpiping failure and dam-breaking as a whole.