修正有限元强度折减法与失稳判据在边坡稳定分析中的应用

现有的有限元强度折减法用于边坡稳定性分析，在土体变形特性的认识和失稳判据上有缺陷。基于土体的应力-应变曲线和邓肯-张非线性弹性模型进行有限元强度折减法计算分析，在现有方法仅对强度参数--黏聚力c和内摩擦角φ进行折减的基础上，提出了切线弹性模量Et的折减算法，更全面地体现折减的内涵；提出了以潜在滑动区域的能量积分变化作为判据，根据能量积分与折减系数关系曲线的特征，将其拟合成两段直线，以其交点所对应的折减系数作为边坡的安全系数。比较分析了修正Duncan有限元强度折减法、失稳判据与文献的计算结果，同时分析了边坡滑动区能量积分计算范围对结果的影响，并用于南水北调东线实际工程计算分析。结果表明：修正Duncan有限元强度折减法能较全面考虑土体的变形和强度特性，新的边坡滑动失稳判据可行且具有较好的计算稳定性，能保证工程建设的安全。

Modified finite element method for shear strength reduction and instability criterion in slope stability analysis

The finite element method for strength reduction recently used in slope stability analysis has disadvantages in revelation of soil deformation behavior and instability criterion. Based on stress strain curves of soil, Duncan-Zhang nonlinear elastic model and direct reduction of strength parameters (cohesion c and friction angle φ) of soil, discount method for tangent modulus Et is presented. The connotation of reduction is entirely revealed. And the exchange of deformation energy in potential slip area is proposed as instability criterion. On the characteristics of relation curve of deformation energy in slip area and reduction coefficient, two straight lines are drawn, the value of reduction coefficient at intersection point of the two lines is choice of safety factor of slope stability. The calculation results by modified Duncan’s finite element method with new instability criterion and references are compared, the influence of calculation area on deformation energy is analyzed, the new method is used in slope stability analysis of south channel of East line in South-to-North Water Diversion Engineering. All results show that the soil behaviors of deformation and strength are more entirely considered in modified Duncan’s finite element method for shear strength reduction, new instability criterion of slope is reliable and calculation is steady; safety of slope construction can be ensured.