考虑地震与溃坝洪水共同作用的土石坝坝坡稳定分析方法

Analysis method for the slope stability of earth-rock fill dam considering the effect of concurrent earthquake and dam-break flood

地震与洪水作用是影响土石坝坝坡稳定的主要因素,在梯级水库中,上游溃坝洪水的影响尤为显著。以上一梯级溃坝洪水引起的坝前水位变化模拟洪水作用,提出在毕肖普法基础上,考虑坝体材料变异系数,大坝遭遇上游溃坝洪水与地震共同作用时的坝坡稳定分析方法。以"卜寺沟-双江口"两梯级为例,假定卜寺沟发生溃坝,进行下游梯级"双江口"下游坝坡稳定的可靠度风险分析。计算结果表明,双江口在遭遇上游溃坝洪水和地震的极端情况下,下游坝坡失效概率为1.571×10^(-6),对应的可靠度指标为4.667,满足规范对I级建筑物发生二类破坏的要求。

Earthquake and flood are the major factors which affect the slope stability of earth-rock fill dam in cascade reservoirs, and the effect of dam-break flood from upstream is especially remarkable. Analysis method was put forward for the earth-rock fill dam slope stability considering the effect of concurrent earth- quake and dam-break flood. The method is based on the Bishop method, considering the variation coeffi- cient of dam material, and the effect of dam-break flood is modeled by the fluctuation of dam front water level. Taking ＂Busigou-Shuangjiangkou＂ two ascades as an example, the dam slope stability and the risk of the downstream cascade dam slope of ＂Shuangjiangkou＂ were analyzed. The results show that, under the extreme condition of dam-break flood from upstream and earthquake, the downstream dam slope failure probability is 1.571×10-6, and the corresponding reliability index is 4.667. The stability meets the standard requirements for the second class destruction of the first-grade structure.