库岸边坡在不同水位下降模式下的稳定性分析

Stability Analysis of Reservoir Bank Slope under Different Water Level Decline Modes

摘要:

通过引入瞬态饱和/非饱和渗流模型,结合有限元强度折减法(SR-FEM),精确评估库岸边坡在水位下降过程中的稳定性，以弥补传统方法在水位变化条件下安全系数估算不足的问题。利用SR-FEM对全缓降和全快降条件下的边坡稳定性进行基准测试,并与极限平衡法(LEM)结果进行对比。再建立瞬态饱和/非饱和渗流模型,详细考察潜水面位置、水位下降比、水位下降速率、导水率及基质吸力等因素对岸坡稳定性的影响。研究表明,在高导水率土体中，孔隙水压力和安全系数(FOS)对压降速率的敏感性显著;低导水率及中高降水率或高导水率与高降水率组合条件下，边坡行为更趋近于完全快速降水模式。此外,随着降水速率或降水比的增加,FOS显著降低;考虑非饱和区基质吸力后,FOS略有回升。瞬态饱和/非饱和渗流模型结合有限元强度折减法能够更为真实地反映边坡在水位下降过程中的复杂应力-渗流耦合效应,为库岸边坡稳定性评估提供了更为精准和全面的方法。

Abstract:

This paper aims 1o accurately evaluate the stability of reservoir bank slopes during water level decline byintroducing a transient saturated/unsaturated seepage model, combined with the finite element strength reduction method(SR-FE， M), so as to make up for the deficiency of traditional methods in estimating the safety factor under water levelchange conditions. The SR-FE.M is used to conduct benchmark tests on slope stability under the conditions of full slowdrop and full fast drop, and the results are compared with those of the limit equilibrium method (LE'M). Then,a transientsaturated/unsaturated seepage model is established to investigate in detail the influences of factors such as phreaticsurface position, water level drop ratio, water level drop rate, hydraulic conductivity, and matrix suction on bank slopestability. The research shows that in soils with high hydraulic conductivity,the pore water pressure and factor of safely(FOS) are signilicanly sensitive to the pressure drop rate; under the conditions of low hydraulic conductivity combinedwith medium-high water level drop rate, or high hydraulic conductivity combined with high water level drop rate, theslope behavior is closer to the complete rapid water level drop mode. In addition, with the increase of water level drop rateor drop ratio, the FOS decreases significantly; after considering the matrix suction in the unsaturated zone, the FOS risesslightly.The transient saturated/unsaturated seepage model combined with the finite element strength reduction methodcan more truly rellect the complex stress-seepage coupling effect of the slope during water level decline, providing a moreaccurate and comprehensive method for the stability evaluation of reservoir bank slopes.