三峡库区卧沙溪滑坡变形特征与机制

三峡水库蓄水后大量涉水老滑坡产生复活变形,其中卧沙溪滑坡是三峡库区典型滑坡之一,自2003年水库蓄水以来一直持续变形,变形位移呈现出一定的周期性和阶跃性。根据宏观地质调查及专业监测资料,分析滑坡变形演化特征,得到滑坡变形的影响因素及变形机制。砂泥岩互层的软弱地层为滑坡的复活变形提供了物质基础,良好的地形则为滑坡持续变形提供了微地貌条件。通过理论分析与数值模拟计算可知,滑坡复活变形的最主要影响因素则是库水位波动,受库水位下降时饱水加载效应和动水压力效应的影响,坡体内形成巨大的指向坡外的渗透压力,导致坡体稳定性急剧下降产生显著变形。该滑坡次级滑体目前处于欠稳定状态,若加大库水位下降速率,则处于不稳定状态。研究结果为滑坡防治及水库调度提供了依据。

Deformation and failure mechanism of Woshaxi landslide in Three Gorges reservoir area

With the operation of the Three Gorges reservoir,many of the old landslides were newly deformed.The Woshaxi landslide was one of the typical landslides in the Three Gorges Reservoir area,which had been continuously deformed since 2003 and the deformation showed a certain periodicity and regularity.According to the geological survey and professional monitoring data,the landslide deformation characteristics were analyzed,and the influence factors and deformation mechanism were obtained.The results show that the sandstone mudstone and topography provided conditions for landslide deformation.The main factor affecting the deformation was the reservoir water level fluctuation which had saturated loading effect and hydrodynamic pressure effect when the water level dropped down.A huge seepage pressure was formed to the outside of the slope,which resulted that the stability of the slope decreased and the deformation produced.The secondary sliding body is in an unstable state and if the rate of water level increases it will be in an unstable state.Studies provide a basis for the landslide monitoring,early warning and prevention,as well as the reservoir operation.