基于容重增加与强度折减法的边坡稳定性对比分析

Contrast Analysis of Slope Stability Based on Gravity Increase and Strength Reduction Method

为了研究容重增加法在边坡稳定分析中的适用性及计算精度,针对一算例边坡采用非线性的有限元法进行数值模拟。基于ANSYS分析软件自带的外接圆D-P准则和非关联的流动法则,以坡顶水平位移的突变和等效塑性应变区域的贯通作为边坡失稳判据,运用容重增加法求出稳定安全系数。然后利用安全系数转换公式计算出不同D-P准则下的安全系数,将其与强度折减法和极限平衡法计算结果进行比较,发现容重增加法较极限平衡法和强度折减法计算结果偏大。在此基础上对影响计算精度的坡比、黏聚力、内摩擦角、计算网格大小等因素进行了敏感性分析。结果表明:各因素对容重增加法的计算精度影响均大于强度折减法。当抗剪强度指标较小而坡度较陡时,容重增加法计算结果较为可靠。相比较而言,强度折减法计算结果合理实用,而容重增加法的应用存在一定的局限性。

In order to study on the application and calculation precision of gravity increase method in the analysis of slope stability, the example slope is numerically simulated using nonlinear FEM, with employment of non-associated flow rule and circumcircle Drucker-Prager （D-P） yield criterion provided by the ANSYS programme. The safety factor of slope stability is calculated by using gravity increase method according to the horizontal deformation catastrophe of slope top and the connectivity of equivalent plastic strain zone. Then the safety factor could be obtained under different D-P yield criterion based on the conversion formula. Through comparing with the calculation results of limit equilibrium and strength reduction method, it is found that safety factor obtained by using gravity increase method is larger than that obtained by strength reduction method and limit equilibrium. On this basis, the factors affecting calculation precision such as slope ratio, cohesion, internal friction angle and size of computational grid, are analyzed. The results indicate that effect of calculation precision by various factors, with gravity increase method is higher than that strength reduction method and the calculation results using gravity increase method are more reliable when soil shear strength index values of steep slope are small. By comparison, the results calculated by strength reduction method is reasonable and practical, while the application of gravity increase method has certain limitations in evaluating slope stability.