基坑抗隆起稳定三维分析的极限平衡法

A Three-Dimensional Limit Equilibrium Method for Basal Stability Analysis

目的优化基坑抗隆起设计,提出适合于基坑抗隆起的稳定的三维分析方法,指导施工,节约工程投资.方法在圆弧滑动法的基础上,假设基坑滑裂块体为一个柱状体,该柱状体的滑裂面包括圆弧滑裂面、柱状体两端的滑裂侧面.基坑的隆起立柱主要包括滑裂块体的自重和基坑围护结构旁边的地面超载,抗隆起力矩主要是由滑裂块体的圆弧滑裂面和其两端滑裂侧面的土体强度提供.结果基坑三维抗隆起稳定分析的计算结果要大于传统的基于二维的抗隆起稳定系数,并且在基坑的计算长度与圆弧半径越接近时这种效果越明显.结论是基坑的抗隆起稳定计算应该要考虑土体的空间效应,通过对上海市轨道交通四号线修复工程中的中基坑、西基坑实例验算,抗隆起稳定安全系数分别1.951分别增加到3.2321,2.424,实际也验证了考虑空间三维效应计算方法的合理性.

In order to optimize the design of braced foundation pits, we propose a three-dimensional limit equilibrium method which is more suitable for basal stability analysis, guiding the construction, and saving the investment. Based on circular slide method, assuming the slip block is a cylindrical body, and the surface of this slip block includes one arc slip surface and two side faces of this cylinder, the sliding moment provided by the weight of this slip block and ground overload, the anti-sliding moment provided by the soil strength of slip surface which comprise arc slip surface and two side faces of this cylinder. Then, the calculation results from this paper are bigger than those from the traditional two-dimensional circular slide method and show more significant when the calculating length is close to arc radius. Finally basal stability analysis should take account the spatial effect of said,on the 4th of Shanghai Metro Line restoration of the Middle,west pit checking,the factor of safety was increased from 1. 951 to 3.2321,2. 424 respectively. It is also verified the rea- sonable of this calculated.