某水库水位的下降对坝体边坡稳定性的影响

水位下降时，一方面坝体内部渗流场会发生变化，土体基质吸力也相应地改变；另一方面，坝体内部土体孔隙水压力、强度参数随水位变化也会改变。因此，库水位变化对边坡安全系数有重要的影响。基于geo-studio软件中的slope/w和seep/w模块来模拟库区水位线的降低和基质吸力对边坡稳定性的影响。结果表明：当水位快速下降的时候，坝体中水位没有相应降低，孔隙水压力没有及时消散，强度参数C、 φ几乎不变，但坝体外部水压力降低，其速率越快，边坡安全系数下降得越明显；水位线缓慢下降时，坝体内部孔隙水压力消散和外部水位线发生同步变化，随着坝体孔隙水压力的消散，坝体内部土体有效应力增加，边坡安全系数逐渐增大，边坡的稳定性相应地变好；与此同时，当坝体内部土体呈饱和状态时，基质吸力为零，基质吸力对边坡稳定性几乎没有影响，随着土体内部水位线的降低，土体由饱和状态逐步变为不饱和状态，基质吸力逐渐增大，坝体的安全系数又逐渐升高，稳定性也随之增强。

The Impact of Dam Water Level Decline on Slope Stability of a Dam

When the water level declines，the seepage field within the dam will make change，and the matric suction of the soil will also change correspondingly.On the other hand，the pore water pressure and the strength parameters will also vary with the water level.So，the variation of water level has an important influence on the slope safety factor.The slope/w and seep/w modules from geo-studio software are adopted to simulate the decline of water level in the dam and the impact of matric suction on the slope stability.The result shows that: when the water level rapidly falls down，the water level within the dam does not decrease correspondingly，the pore water pressure is not dissipated in time，and the strength parameters C,φ almost keep the same.However，the faster the pore water pressure outside the dam falls down，the more obviously the slope safety factor decline.When the water level decline slowly，the dissipation of the pore water pressure in the dam keeps pace with the water level outside the dam.With the dissipation of pore water pressure，the effective stress of the soil inside the dam increases，and the factor of slope safety gradually rising，the stability of slope will also become better correspondingly.Meanwhile，when the soil inside of the dam is saturated，the matric suction is zero.There is no influence of matric suction on the slope stability.With the water level dropping down in soil，the saturated soil varies into the unsaturated state.The matrix suction begins to increase gradually，the safety factor of dam body will rise again，and the slope stability is also improved with it.