利用有限元强度折减法进行渗流条件下的基坑整体稳定性分析

Integral stability analysis of foundation pits under seepage by using FEM strength reduction

渗流作用下的基坑稳定性分析一直是基坑工程中的难点。传统基坑设计方法在计算基坑整体稳定性时存在以下问题:不考虑降水方式和渗流对基坑整体稳定性的影响,不管什么情况都假定圆弧滑动面破坏等。结合算例介绍了应用PLAXIS有限元程序模拟降水条件下的深基坑开挖过程,并通过有限元强度折减法计算得到了基坑整体稳定安全系数。计算结果表明:潜水位生成水压、渗流计算生成水压以及基坑外水位不降3种工况下,基坑整体稳定安全系数差别较大;PLAXIS程序根据有限元强度折减法分析得到的滑动面比传统设计方法中假定的圆弧滑动面更加合理,因此应用具有渗流计算功能的PLAXIS程序计算得到的基坑整体稳定安全系数更为准确合理。

The traditional method for design of foundation pits has unresolved issues in calculation of the integral pit stability. The influences of precipitation pattern and seepage on the stability are not taken into consideration, and a circular sliding surface is assumed under all circumstances. In the present study, the excavation of deep foundation pit under rainfall conditions imitated by using the FEM is considered and the stability safety factor of foundation pit is analyzed by using FEM strength reduction. The calculation results show that there are great differences in the safety factors under three different conditions. The water pressure is caused by groundwater seepage, and the water level outside the foundation pit does not drop. The sliding surface obtained by using PLAXIS software with FEM strength reduction is more reasonable than the assumed circular sliding surface in the traditional method.