HD水电站库岸大型斜坡变形体成因机制及稳定性评价

Genetic Mechanism and Stability Evaluation of Large Slope Deformation Body on Reservoir Bank of HD Hydropower Station

近年来,受水库蓄水及降雨等因素影响,造成大量水电站库岸边坡变形加剧,一旦失稳极可能对电站的正常运行造成极大危害。选取距HD水电站坝址约6 km,方量约353×10^(4)m^(3)的库岸边坡变形体作为研究对象,通过综合采用野外地质精细调查、室内试验、三维数值模拟和理论分析等方法对该变形体的稳定性及成因机制进行深入研究。结果表明:该岸坡变形体基岩以玄武岩、凝灰岩为主,覆盖层总体较薄,主要为碎石土,变形体的持续发育由多因素耦合作用引起;当暴雨或水库蓄水时,变形体有效应力减小,位移量增加,滑面剪应变增量增加且贯通性更好;三维数值模拟结果显示,在天然、暴雨、低蓄水位(1586 m)和高蓄水位(1691 m)工况下的最大变形量分别为33.9、56.2、79.5、88.6 cm;该变形体的发育过程可分为两个阶段,分别是天然情况下的稳定阶段和暴雨或水库蓄水后的加速变形阶段,暴雨和库水位上升是促进该变形体持续变形的主要原因。

In recent years,due to the influence of reservoir water storage and rainfall,the slope deformation of a large number of reservoirs has intensified,and once the instability is likely to cause harm to the normal operation of the hydropower station.A deformable body on the bank slope of a reservoir,about 6 km away from the dam site of HD Hydropower Station,with a volume of about 3.53×10^(6)m^(3),was selected as the research object,and the stability and genetic mechanism of the deformable body are deeply studied by comprehensive methods of field geological investigation,laboratory tests,three-dimensional numerical simulation and theoretical analysis.The results show that the bedrock of the metamorphic rock is mainly basalt and tuff,and the overlying layer is generally thin and mainly gravel soil.The continuous development of the metamorphic rock is caused by the coupling of multiple factors.The effective stress of the deformable body decreases,the displacement increases,the shear strain increment of the sliding surface increases and the permeability is better when the rainstorm or reservoir is filled.The 3D numerical simulation results show that the maximum deformation under natural conditions,heavy rain,low water level(1586 m)and high water level(1691 m)is 33.9 cm,56.2 cm,79.5 cm and 88.6 cm,respectively.The development process of the deformable body can be divided into two stages,which are the stable stage under natural conditions and the accelerated deformation stage after heavy rain or reservoir filling,indicating that heavy rain and the rise of reservoir water level are the main reasons to promote the continuous deformation of the deformation body.