水位骤降时的非饱和坝坡稳定分析

Analysis of stability of dam slope during rapid drawdown of reservoir water level

从非饱和土抗剪强度理论出发,应用极限平衡法和以有限元应力计算为基础的极限平衡法,分别对库水位骤降时的坝坡稳定进行了计算。分析中采用非饱和-非稳定渗流理论,模拟了孔隙水压力的消散过程,并考虑基质吸力对土体抗剪强度的影响,将每个渗流分析结果调入稳定分析模块计算其稳定性。最后将两类极限平衡法稳定分析结果进行了比较,结果表明,库水位的骤降,易引起坝坡的滑动,随着超静孔隙水压力的消散,坝坡稳定性逐渐提高;随着孔压消散,基质吸力对抗剪强度的贡献增大。

The stability of dam slope during rapid drawdown of reservoir water level was computed using limit equilibrium method and limit equilibrium method based on finite element analysis according to unsaturated soil shear strength theory in combination with a specific reservoir.In this computing process,the dissipating process of pore-water pressure was simulated using unsaturated-unsteady seepage theory and the impact of matric suction on shear strength of soil body was taken into consideration,each step of seepage corresponding to a stable situation of the dam.Finally,the comparison between both of stability analysis methods was made.It is found that the rapid drawdown of reservoir water level easily results in the dam slope slipping;the stability of dam slope is enhanced with the dissipating process of water pressure in the dam body;and the matric suction increases the shear strength in this dissipating process.