Transient seepage characteristics of earth-rock dams and the influences on stability against slide of dam slope during reservoir water level drawdown
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.
reservoir water level drawdowntransient seepagestability of dam slopesafety factorfailure probability
NETL
NSTL
万方数据
