浮托减重效应对三峡库区竹林湾滑坡稳定性影响研究

Study of Buoyancy Effect on Stability of Zhulinwan Landslide in Three Gorges Reservoir Area

由于水库水位上升产生的浮托减重效应,三峡库区自从2003年蓄水后,特别是在2008年首次进行175 m试验性蓄水时大量滑坡发生复活并变形.此后在历年的水位上升阶段,又再次产生这种周期性和间歇性的变形,奉节县的竹林湾滑坡便是典型滑坡之一,其每年在水位较高时处于缓慢蠕动变形状态,变形随着水位上升而产生,水位下降又逐渐趋于稳定.通过分析竹林湾滑坡的变形演化过程及其与降雨、库水位变动等因素的耦合关系,借助数值模拟计算,可得到以下结果:滑坡的砂泥岩互层岩性及微地貌特征为滑坡的变形提供了良好的地质基础,降雨对滑坡的稳定性影响很小,滑坡变形诱发条件为库水位的上升,数值模拟的渗流与稳定性计算结果显示,库水位持续上升导致滑坡稳定性不断减小,当水位升至175 m时,滑坡稳定性系数随后也达到最小值,随着变形的演化发展,可能由缓慢变形最终导致失稳破坏,这与实际变形结果基本吻合,该研究结果为水库水位调度提供了相关参考和依据.

As a result of the buoyancy effect caused by the rise of reservoir water level,a large number of landslides have been revived and deformed since the impoundment of the Three Gorges Reservoir in 2003,especially during the first experimental impoundment of 175 meters in 2008.This periodic and intermittent deformation occurred again in the rising stage of water level over the years.The Zhulinwan landslide in Fengjie County is one of the typical landslides.Due to the buoyancy effect caused by the rise of reservoir water level,the Zhulinwan landslide is in a slow creeping deformation state every year when the water level is high.Its deformation occurs with the rise of water level,and tends to be stable when the water level decreases gradually.By studying the response mechanism of landslide deformation with fluctuation of water level,the coupling relationship between reservoir water level,rainfall and landslide deformation is analyzed;then and the following results are obtained by numerical simulation.The lithology of Jurassic sandstone provides a material basis for landslide and micro topography provides good conditions for landslide displacement,The induced factor of landslide deformation is the rising of reservoir water level.The numerical simulation results of seepage and stability show that the stability of landslide decreases with the rising of reservoir water level.When the water level rises to 175 m,the factor of safety of landslide also reaches the minimum.With the evolution of deformation,slow deformation may eventually lead to instability and failure.The research results provide basis for landslide prevention and control and reservoir operation.