开挖边坡的三维有限元稳定分析

Stability Analysis of Soil Excavation by 3D FEM

用强度折减有限元方法对开挖边坡进行了三维稳定性分析.计算结果表明:对于约束效应不明显的开挖边坡,边坡的初始破坏面在边坡的中部,随着折减系数的增大,边坡的破坏由边坡中部向两侧扩展,最终边坡在空间上形成匙状或贝壳状的立体土体破坏;当边坡的纵向长度与开挖深度的比值大于4时,边界约束条件对边坡稳定安全系数影响不大,可以近似地按平面应变问题进行分析;对于角部约束效应明显的开挖边坡,当边坡中部剖面发生破坏,边坡角部剖面几乎也同时达到破坏,其稳定安全系数是按平面问题分析结果的1.3倍多,类似的实际问题如果按二维平面应变方法进行分析,其计算结果应用于工程设计中是偏于保守的.

An elastoplastic shear strength reduction FEM is used to analyze the 3D stability of the excavation slope. For the excavation slope with the weak constraint condition, the location of the initial failure plane is in the middle of the slope. With the increment of the factor of strength reduction, the slope failure zone is extended to the sides of the slope. When the ratio of the excavation length to the height is more than 4, the factor of safety of the slope less affected by constrained boundaries is approximately the same as that of plane strain stability analysis. For the excavation slope with the obvious corner effect, each section of the slope almost reaches failure simultaneously. The factor of safety of the slope is larger than that of plane strain stability analysis. If the above problem is analyzed by the 2D plain strain method, the result will be conservative for the design of proiect.