为研究坝基中存在多条软弱夹层的复杂地基重力坝的深层抗滑稳定问题,运用ANSYS有限元软件,建立了某水库工程重力坝-坝基系统的有限元模型。采用超载降强综合法,即同时考虑水荷载和坝基材料因素变化的作用,并结合突变理论,分别建立了特征点水平位移和坝基中软弱夹层上下点相对位移与综合系数的尖点突变模型,并通过建立模型的标准势函数,根据其判别式的正负来判断重力坝是否失稳。为了更好地表征结构的性态转变,应采用恰当的突变指标,比如坝基中软弱夹层上下点相对位移指标,得出抗滑稳定安全系数在区间[3.125,3.188]内,与传统刚体极限平衡法得到的安全系数在区间[3.039,3.667]内相一致,同时为了更精确地进行失稳判别,应结合其他判据,并建立综合的判别体系。

There are several weak structural planes in some gravity dams with complex foundation, which will affect the anti-sliding stability of deep layer. In order to explore the problem, we establish a finite element model of gravity dam-foundation system for a reservoir project by using finite element software of ANSYS. We adopt a comprehensive method of overload and strength reduction, considering water load and the change of material factor at the same time. Then, in association with cusp catastrophe theory, we obtain the variations of horizontal displacement at feature points and relative displacement between upper and lower points of weak interlayer with comprehensive coefficient. By establishing the standard potential function of the model, we can judge that gravity dam is instable or stable according to the function’s discriminant. In order to represent structure state better, we should adopt proper index such as the relative displacement between upper and lower points of weak structural plane. Anti-sliding stability coefficient of the example is within the range of [3.125,3.188] by using the comprehensive method, while in traditional rigid limit equilibrium method, the range is [3.039,3.667], so the two ranges are similar. For more precise identification of instability, we should combine criteria mentioned with other criteria and develop a comprehensive evaluation system.