三维边坡稳定性分析中的边界约束效应

边界约束条件是影响边坡强度折减有限元分析稳定性计算结果的一个重要因素。结合典型边坡算例计算给出了不同边界约束条件下的三维边坡稳定性安全系数及潜在滑动面，并进行了差异性的对比研究,最后结合存在软弱夹层与地下水的三维边坡开展了应用性研究。结果表明：边界约束条件对边坡稳定安全系数具有显著的影响。在全约束条件下安全系数最大，其次为半约束边界条件，自由边界条件下的稳定安全系数最小，全约束边界比自由边界条件下的安全系数提高大约30%。边界约束条件对边坡潜在滑动面有重要的影响。在土性参数完全相同的条件下，与全约束条件相比，半约束边界条件下的滑体体积更大，滑动面更深，滑出点位置从离坡脚不远处向坡脚变化的过程更加明显。自由边界条件下与二维计算结果较接近。

Effect of Boundary Constraint Condition on the Stability Analysis of 3D Slope

Boundary constraint condition is one of the most important influencing factors in 3D stability analysis based on shear strength reduction finite element method(SSR-FEM). A typical three-dimension slope case is adopted to study safty factor and potential sliding surface under various boundary constraint conditions, and their difference is discussed. Then, the results of a 3D slope case with soft interlayer and groundwater are illustrated using SSR-FEM. The results indicates that the boundary constraint conditions have a remarkable effect on the slope stability, the fixed constraint in three directions effect is the largest one, free constraint effect is the smallest one. Moreover, the boundary constraint conditions have also a certain effect on the potential sliding surface of three dimensional slope. The effect is related to the ratio of length and height for the slope. When the ratio of length and height for the slope is larger than 8 (L/H>8), the location of slip surface and out-slip points in 3D slope is very similar to that from 2D plane strain analysis. So the ratio of L/H=8 can be taken as the limit point for 2D and 3D stability analysis in SSR-FEM.