基于强度折减法的圆形深基坑坑底抗隆起稳定性分析  

Strength reduction approach for analyzing safety against basal heave of circular deep excavations

作　　者：王卫东[1] 徐中华[1] 

机构地区：[1]华东建筑设计研究院有限公司地基基础与地下工程设计研究所,上海200002

出　　处：《建筑结构学报》2010年第5期195-201,共7页Journal of Building Structures

基　　金：上海市优秀学科带头人计划项目(07XD14206);上海市科委重点攻关项目(08201200901)

摘　　要：用于一般形状基坑的坑底抗隆起稳定分析方法因不能考虑圆形基坑环向土体挤压作用而不适合于圆形基坑的分析。基于非线性有限元提出了轴对称条件下基坑坑底抗隆起稳定分析的强度折减方法。研究表明:圆形基坑强度折减到破坏时的滑裂面形状与一般形状基坑的滑裂面形状相似,但圆形基坑的滑裂面并不通过围护墙墙底,而是通过墙底下方的土体。采用平面轴对称有限元的强度折减法分析得到的坑底抗隆起稳定系数较平面应变有限元强度折减分析得到的稳定系数高得多。当开挖深度很小时,圆形基坑具有较大的坑底抗隆起稳定系数;但其值随着开挖深度的增大而逐渐减小。圆形基坑的坑底抗隆起稳定系数随着围护墙插入比的增大呈线性增加。最后采用基于平面轴对称有限元的强度折减法分析了上海世博500kV地下变电站圆形基坑的坑底抗隆起稳定性。The methods which are used for analyzing the factor of safety against basal heave（FS） for regular rectangular excavations are not suitable for analyzing circular excavations as the effect of intermediate principal stress is not considered in these methods.The strength reduction approach based on non-linear axi-symmetric FEM was proposed to calculate the FS of circular excavations.The shape of slip surface at failure obtained by axi-symmetric FEM was similar to that obtained by plane strain FEM.However,the former passes through the soil under the wall toe while the latter passes through wall toe.Factor of safety against basal heave obtained by axi-symmetric FEM is far larger than that obtained by plane strain FEM.The FS is quite large when excavation depth is small.However,it decreases with the increase of excavation depth.It is found that the FS roughly linearly increases with the increase of embedded depth ratio of retaining wall.Finally,the strength reduction approach based on non-linear axi-symmetric FEM was adopted to analyze the safety against basal heave of the Shanghai 500kV World Expo Underground Transmission and Substation excavation.

关 键 词：圆形深基坑 强度折减法 有限元分析 坑底抗隆起稳定分析 

分 类 号：TU476.3[建筑科学—结构工程] TU470.3[建筑科学—土工工程]