土坝在水库水位下降期的滑坡机理

采用有限元法模拟土坝在水库水位下降过程中的瞬态渗流，在此基础上采用极限平衡法计算土坝临水坡的稳定性。通过时均质土坝和心墙土坝的时比研究，揭示了坝体土料性质、水位降落过程线特征与土坝孔隙水压力之间的关系及其在坝坡失稳时所起的作用。研究结果还表明：基于稳定渗流分析的坝坡稳定分析不能考虑孔隙水压力、渗流动水压力的变化及其时坝坡稳定性的影响，因而不能准确评估水库水位下降条件下土坝临水坡的稳定性。

Mechanism of Earth Dam Landslide during Reservoir Water Level Descending Period

In this paper, Finite Element Method (FEM) is applied in the simulation of transient seepage of earth dam during reservoir water level descending period, and the stability of earth dam water-facing slope is calculated by using Limit Equilibrium Method on the basis of the simulation. Through comparison of homogeneous earth dam and core-wall earth dam, the relationship between water level descending process characteristics and pore water pressure of earth dam and the effect on the earth dam instability are revealed. The results also show that earth dam slope stability analysis based on stable seepage process fails to consider the changes in pore water pressure, seepage dynamic water pressure and their influences on dam slope stability, thus it cannot accurately assess the stability of earth dam water-facing slope under conditions of reservoir water level descending.