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水库水位骤降会对土石坝渗流、变形和稳定产生较大影响,若此时偶遇地震,则可能对大坝安全构成新的威胁。结合某拟建300 m级超高心墙土石坝,对其进行库水位骤降时的大坝非恒定、饱和–非饱和渗流场分析,获取静孔隙水压力。在渗流场和静应力场耦合计算基础上考虑地震偶遇作用,对大坝进行地震反应分析,并从坝坡抗震稳定和坝体永久变形方面进行大坝抗震安全分析评价。研究表明:对于具有良好防渗性能的心墙并有上游反滤安全保护的高心墙堆石坝,库水位骤降主要影响心墙及上游堆石坝体的孔隙水压力分布,使震前坝体上游区域的静力平均有效应力场有较大改变。此时偶遇地震作用,大坝上游区域的动力反应及上游坝坡抗震性能变化较大,需引起注意。库水位的变化基本未对下游堆石坝体的渗流场分布产生明显影响,因而库水位骤降对下游坝体抗震安全影响甚微。
The sudden drop of reservoir water level will greatly affect seepage, deformation and stability of earth-rock dams. If an earthquake happens at this time, it may pose a new threat to dam safety. Combined with a proposed 300 m ultra-high core earth-rock dam, the unsteady, saturated-unsaturated seepage field analysis of the dam during the sudden drop of the reservoir level is carried out to obtain the static pore water pressure. Based on the coupling calculation of seepage field and static stress field, the accidental seismics are considered to analyze the seismic response of the dam. The dam seismic safety analysis and evaluation is carried out based on the seismic stability of the dam slope and the permanent deformation of the dam. The results show that for the high core rockfill dam with well impervious core wall and upstream filter protection and safety protection, the sudden drop in reservoir water level mainly affects the distribution of pore water pressure in the core and upstream rockfill dam, The static average effective stress field in the upstream area of the dam body is greatly changed. In this case, the earthquake response is encountered. The dynamic response in the upstream area of the dam and the seismic performance of the upstream dam slope vary greatly, which needs attention. The change of reservoir water level basically has no obvious influence on the seepage field distribution of downstream rockfill dam, so the sudden drop of reservoir water level has little effect on the seismic safety of downstream dam.