库水下降下土石坝瞬态渗流特性及渗流对坝坡抗滑稳定影响  

Transient seepage characteristics of earth-rock dams and the influences on stability against slide of dam slope during reservoir water level drawdown

作　　者：李邓军 任旭华[1] 岑威钧[1] 刘波 LI Dengjun;REN Xuhua;CEN Weijun;LIU Bo(College of Water Conservancy and Hydropower Engineering,Hohai University,Nanjing 210098,China)

机构地区：[1]河海大学水利水电学院,江苏南京210098

出　　处：《武汉大学学报（工学版）》2024年第4期420-426,共7页Engineering Journal of Wuhan University

摘　　要：库水位变化引起的瞬态渗流对土石坝坝坡稳定性影响显著,为此依托某土石坝工程,开展不同库水位下降速率和坝体渗透性下大坝瞬态渗流场计算,分析坝体浸润线滞后程度及上游坝面渗流量变化特性,进而在考虑坝体材料抗剪强度随机分布的基础上对坝坡开展瞬态渗流作用下的抗滑稳定性分析,获得坝坡稳定安全系数及失稳概率变化曲线。计算结果表明:库水位下降速率v越大,坝体渗透系数ks越小,浸润线的滞后程度越显著;v越大或ks越大,到达稳定降落水位时的外渗流量越大;库水位下降结束瞬时坝体浸润线滞后率最大,使得坝坡稳定安全系数最小,相应的失稳概率最大,随着时间延续安全系数会不断回升,失稳概率相应降低;建立的坝坡稳定安全系数和失稳概率与浸润线滞后率的拟合关系式可为综合评估大坝运行安全提供理论指导。Transient seepage caused by the change of reservoir water level has a significant influence on the stability of slope of earth-rock dams.Based on an earth-rock dam project,the transient seepage field of the dam is calculated under different water level decline rates of reservoir and dam permeability.The hysteresis degree of phreatic lines and the change characteristics of upstream dam surface seepage are analyzed.Then,the stability against slide of upstream dam slope under the action of transient seepage is analyzed based on the random distribution of shear strength of dam materials,and the variation curves of the stability safety factor and failure probability of the upstream dam slope are obtained.The calculation results indicate that the hysteresis degree of the dam phreatic line increases significantly with the increase of water level decline rate(v)of reservoir or with the decrease of dam permeability coefficient(ks).With the increase of v or ks,the drainage discharge increases when the reservoir reaches the stable falling water level.At the end of drawdown of reservoir water level,the instantaneous hysteresis rate of dam phreatic line is the largest,the safety factor of dam slope is the smallest,and the failure probability is the largest.With the extension of time,the safety factor will continue to rise and the failure probability will decrease accordingly.The established fitting relations between safety factor of dam slope stability and the failure probability and hysteresis rate of dam phreatic line can provide theoretical guidance for the comprehensive evaluation of dam operation safety.

关 键 词：库水位下降 瞬态渗流 坝坡稳定性 安全系数 失稳概率 

分 类 号：TV641.2[水利工程—水利水电工程]