库水位+降雨条件下四方井粘土心墙坝坝坡渗透稳定可靠度分析

针对粘土心墙坝坝坡稳定仅局限于确定性分析,考虑到尚缺乏研究坝体材料空间变异性的问题,以四方井水库粘土心墙坝为例,对库水位联合降雨工况下的坝坡渗透稳定性进行数值模拟,同时基于Monte-Carlo法分析了可靠度规律。结果表明,单纯的库水位骤降监测点孔压随时间呈单调下降趋势,库水位骤降速率越大,孔压下降速率越快。降雨联合库水位工况在降雨时刻孔压有一个突升的过程;库水位骤降情况下安全系数随库水位下降呈先下降后上升最终保持不变,库水位骤降速率越大,最小安全系数越小,出现的时间亦越早;不同类型降雨工况安全系数在降雨过程中有一个突降的过程,最终安全系数回升至初始值,其中后峰型降雨安全系数降幅最大,前锋型降雨安全系数降幅最小;降雨发生在库水位骤降后期最为危险,最小安全系数也越小;库水位骤降情况平均失效概率约为30%,不同类型降雨条件下平均失效概率基本小于10%,降雨发生在库水位骤降不同时刻下失效概率平均约为60%。对降雨发生在库水位后期的情况应加强监测,防止坝坡失稳灾害的发生。

Reliability Analysis of Seepage Stability of Slope with Combined Rainfall and Water Level of Clay Core Dam and Reservoir in Sifangjing

In view of the fact that the slope stability of clay core dam is limited to deterministic analysis, the research on the spatial variability of dam material is still blank. Based on the engineering background of clay core wall dam of Sifangjing Reservoir, the seepage stability of dam slope under combined rainfall condition of reservoir water level is simulated. At the same time, the reliability law is analyzed based on the Monte-Carlo method. The results show that the increase of the water level drop rate and the faster the pore pressure drop rate are the tendency of the pore pressure of the simple reservoir water level dip monitoring points to decrease monotonically with the time. The water level condition of the combined rainfall reservoir has a process of sudden rise of pore pressure at rainfall time. The safety factor of the water level of the reservoir decreases with the decrease of the water level of the reservoir, and then rises to the final level. The higher the drop rate of the reservoir water level, the smaller the minimum safety factor and the earlier the time it appears. The safety factors of different types of rainfall have a process of sudden drop in the process of rainfall. The final safety coefficient rises to the initial value. Rainfall occurs in the later stage of sudden drop of reservoir water level, and the minimum safety factor is smaller; The average failure probability of sudden drop of reservoir water level is about 30%, the average failure probability of different types of rainfall is basically less than 10%, and the average failure probability of rainfall occurs at different times of sudden drop of reservoir water level is about 60%. Monitoring of rainfall in the later stage of reservoir water level should be strengthened to prevent and control the occurrence of dam slope instability disaster.