库水位条件影响下的大地坪滑坡稳定性分析及运动预测研究

Stability Analysis under Reservoir Water Level Conditions andMotion Prediction of Dadiping Landslide

水库蓄水对库岸型滑坡产生巨大威胁并极可能引起整体滑移破坏,开展不同库水位条件下滑坡稳定性研究意义重大。通过现场地质调查、现场试验、原位监测、理论分析和数值模拟等手段,对湖北恩施峡口塘水电站库区大地坪滑坡在不同库水位条件下的稳定性进行研究。利用现场渗透试验获取的滑体渗透系数,在GeoStudio软件中分析水库运行过程中滑坡地下水位的变化情况,采用数值分析程序FLAC对大地坪滑坡进行数值模拟,分析滑体变形对不同库水位的响应情况,并结合物质点法对滑坡整体破坏运动进行预测。结果表明,地下水位与库水位保持同步,基本没有滞后现象;滑坡稳定性的主控因素为高水位运行;水位抬升不利于滑坡的稳定,特别是高水位的持续运行对滑坡的变形影响更大;由于碎石土渗透性较高,库水位的下降使得滑坡稳定性相较于高水位时有所增加;采用物质点法模拟预测大地坪滑坡体大规模滑移破坏,位移主要分布在中前部,最大水平位移约20 m,文沙公路处最大水平位移约18 m。其研究成果可为库岸型滑坡灾害的风险评价提供科学依据。

Reservoir impoundment poses a great threat to reservoir bank landslides thatare likely to cause overall sliding failure.It is of great significance to study the stability of landslides under differentreservoir water levels.Through field geological survey,field test,in-situ monitoring,theoretical analysis and numerical simulation,the stability of Dadiping landslide was studied in the reservoir area of Xiakoutang hydropower station in Enshi,Hubei Province under different reservoir water levels.Using the permeability coefficient of the landslide obtained from the field permeability test,the change of the groundwater level of the landslide during the operation of the reservoir was analyzed in GeoStudio software.The numerical analysis program FLAC was used to simulate the Dadiping landslide.The response of the landslide deformation to different reservoir water levels was analyzed,and the overall failure motion of the landslide was predicted by the material point method.The results show that groundwater level of the landslide remained synchronized with reservoir levels with essentially no hysteresis.The main controlling factor of the stability of Dadiping landslide was the operating elevation of the reservoir water level;the rise of water level was not conducive to the stability of landslide,especially the continuous operation of high water level had a greater impact on the deformation of landslide.Due to the high permeability of gravel soil,the decrease of reservoir water level makes the stability of the landslide increase compared with that at high water level.The material point method is used to simulate and predict the large-scale slip failure of the landslide.The displacement is mainly distributed in the middle and front part,and the maximum horizontal displacement is about 20 m.Maximum horizontal displacement of movement at Wensha Highway is about 18 m.The research results can provide a scientific basis for the risk assessment of reservoir bank landslide disaster.