库水位变化时陡倾软弱顺层岩质滑坡变形机制

Landslide deformation mechanism of steep weak bedding rock under the variation of reservoir water levels

研究库水位动态变化时陡倾软弱顺层岩质滑坡的变形机制,为库岸滑坡防治及库水调度提供帮助。以四川省大渡河某水电站开顶滑坡为例,通过野外调查资料、库水位及地面监测数据综合分析,研究滑坡结构及变形破坏特征;建立二维地质模型,利用离散元模拟蓄水前后陡倾顺层岩质滑坡变形响应过程,结合有限元进一步分析库水作用下岸坡稳定性变化规律。研究结果表明,岸坡特殊的地质构造和岩性是控制滑坡产生的主要因素,水库蓄水诱发了滑坡的变形,库水位变化进一步加速了变形进程。当库水位以4.8 m/d、3.84 m/d、1.92 m/d的速率上升时,坡体稳定性呈现先增后减的趋势;当以小于0.5 m/d的速率下降时,岸坡变形不明显,但稳定性急剧降低,极有可能增加变形速率,加剧变形,导致大范围失稳破坏。在水库调度过程中,为避免渗流作用对岸坡稳定性的影响,库水位变化应保持在较小的速率平稳运行。

Taking the Kaiding landslide of a hydropower station in Dadu River,Sichuan Province as an example,the structure,deformation and failure characteristics of the landslide were studied through the comprehensive analysis of field survey data,reservoir water level and surface monitoring data.The landslide deformation mechanism of steep soft bedding rock under the dynamic change of reservoir water level is revealed,which provides help for reservoir bank landslide control and reservoir water dispatching.A two-dimensional geological model was established to simulate the deformation response process of steep bedding rock landslide before and after impounding with discrete elements method,and the variation rule of bank slope stability under the action of reservoir water was further analyzed with finite element method.The results show that the special geological structure and lithology of the bank slope are the main factors controlling the generation of landslide.The reservoir impaction induces the landslide deformation,and the change of reservoir water level further accelerates the deformation process.When the reservoir water level rises at the rates of 4.8 m/d,3.84 m/d and 1.92 m/d,the slope stability increases first and then decreases.When the rate of decline is less than 0.5 m/d,the deformation of the bank slope is not obvious,but the stability decreases sharply,which is very likely to increase the deformation rate,aggravate the deformation,and lead to a large range of instability failure.In the process of reservoir dispatching,in order to avoid the influence of seepage on bank slope stability,the change of reservoir water level should be kept at a small rate and run smoothly.