Sarma法在四川云阳鸡扒子滑坡稳定性评价中的应用

APPLICATION OF SARMA METHOD TO STABILITY EVALUATION OF JIPAZI SLOPE, YUNYANG COUNTY, SICHUAN PROVINCE

云阳宝塔滑坡区先后发生了多次滑坡 ,其中鸡扒子滑坡是最近的 1次 ,新滑坡是在旧滑坡的基础上沿旧滑坡面的部分复活。根据对该滑坡体几何形态、物质成分与结构特征及水文地质特征的考察 ,初步认为 ,降水入渗与排水不畅引起的滑坡体内孔隙水压力上升是导致鸡扒子滑坡破坏的主导因素。文中根据极限平衡理论 ,运用VC + +语言编制了Sarma法的计算程序 ,对三峡水库蓄水后鸡扒子滑坡是否可能再次发生滑坡进行了评价 ,指出在滑坡体排水率为 5 0 %与三峡水库水位达 14 5m时为滑坡稳定与否的临界值。通过调整影响滑坡稳定性的主要参数的取值 ,对影响滑坡稳定性的因素进行了动态敏感性分析 ,指出降水入渗、长江水位、滑坡体的排水状况是影响滑坡稳定性的决定因素 ,三峡水库蓄水前应针对此采取相应的工程防治措施 ,才能保证水库蓄水后鸡扒子滑坡不再发生滑动。

Several landslide events have successively occurred at Baota slope area of Yunyang County, Sichuan Province, among which the Jipazi landslide is the latest one. The Jipazi landslide represents partial revival of an old landslide. The total volume of the sliding mass is up to 1.5×10 7m 3 or more, of which about 2.3×10 5m 3 were detached from the slide channel and slided down below the flood level of the Yangtze River, causing a serious danger to the navigation on this river segment and enormous economic losses. Once the Three Gorges Reservoir stores water, the water level of the Yangtze River will be much higher than the current level. As a result, new landslide may revive on the old one. Based on the research on the geometry, material component, structural and hydrogeologic features of the sliding mass, it is preliminarily concluded that the Jipazi landslide was caused by the increasing of pore pressure in the sliding mass due to excessive rainfall infiltration and impeded drainage during the storm. In the light of the limit equilibrium theory, a program of Sarma method is designed to evaluate the stability of the Jipazi sliding mass after the Three Gorges reservoir storing water. The result shows that the critical value of the slope stability is that the water level of the Yangtze River reaches 145m high and the drainage rate of the slope is 50%. The dynamic sensitivity analyses of the factors affecting slope stability are carried out through adjusting the values of some affecting parameters of slope stability. The results show that the rainfall infiltration, the water level of the Yangtze River after the Three Gorges reservoir storing water and the drainage rate of sliding mass are the crucial causes affecting stability of the Jipazi landslide. Little rainfall infiltration, low water level of the Yangtze River and unimpeded drainage in the sliding mass will enhance the stability of the slope. Therefore, corresponding prevention and control measures must be taken before the Three Gorges reservoir stores water.