水位升降对库区非饱和土质岸坡稳定性的影响

针对传统的饱和土理论在分析库岸边坡渗流和稳定问题中存在的不足,以非饱和 饱和渗流分析程序模拟水位升降过程中岸坡内孔压场（包括浸润线以上的基质吸力场）.在此基础上,考虑基质吸力对抗剪强度的贡献及其对安全系数的影响,进行了边坡稳定的极限平衡分析,并对影响岸坡渗流场的主要水力参数进行了敏感性分析.分析结果表明,坡外水位升降时,坡内浸润线及其上的基质吸力场发生显著变化,进而影响岸坡稳定;水位升降过程中,岸坡安全系数的变化规律非常复杂,坡内孔隙水压力、坡外水推力和土体容重对稳定安全系数的贡献规律随水位变化而变化;土体的渗透性能和土 水特征曲线的斜率显著影响了水位升降过程中岸坡稳定安全系数的变化规律.

Influence of reservoir water level fluctuations on stability of unsaturated soil banks

As seepage and stability analysis of a bank slope using traditional theory of saturated soils was often inadequate,unsaturated-saturated seepage analysis was carried out to simulate the change of phreatic surface and pore-water pressures in a bank slope subject to reservoir water level fluctuation.The obtained pore-water pressure fields were then input into a limit equilibrium analysis program to evaluate the change in factor of safety(F_s) with reservoir level.And the contribution of matric suction to shear strength was considered.In addition,parametric studies were also carried out to investigate the influence of key hydraulic parameters on the seepage and the slope stability.The analysis results demonstrated that the reservoir water level fluctuation exerted a significant impact on the pore-water pressures in the bank slope,and hence on the slope stability.The variation of F_s with reservoir water level was quite complicated because the contributions of the pore-water pressures,the thrust of reservoir water and the soil gravity to F_s varied with the reservoir level.The parametric study showed that the values of F_s were sensitive to the change in the saturated permeability(k_s) and the slope of the soil-water characteristic curve(m_w).