基于弹性抗力法的深基坑悬臂支护结构上土压力空间效应分析

THE ANALYSIS OF SPATIAL EFFECT OF SOIL PRESSURE ON CANTILEVER REAINING STRUCTURE BASED ON ELASTIC RESISTANCE METHOD

深基坑是一个具有长度、宽度、深度的三维空间结构体系。现行设计规范中将其简化为二维平面应变问题进行分析计算,不能反映基坑的空间性状和尺寸效应。基于弹性抗力法引入土压力发挥系数的概念,提出了土压力发挥系数的计算方法。提出基坑悬臂支护结构顶部冠梁的水平位移与简支梁受均布荷载作用下的水平位移具有相似的形式,在此基础上计算深基坑悬臂支护结构上土压力发挥系数、支护结构变形和内力的空间分布规律。工程实例计算表明:考虑土压力空间效应得到的基坑变形与实测结果相符合。

A deep excavation is a three-dimensional space structure system which has length and width as well as depth. Usually, it is taken as a two-dimension plane strain problem in the current design code. Consequently, the three^dimensional character and size effect cannot be reflected clearly. To improve this, the concept of a soil pressure utilization factor is proposed and the calculation method of the factor is established based on the elastic resistance method. First, the form of horizontal displacement curve of the top beam on a cantilever retaining structure is assumed to be similar as that of a simple beam under distributed load. On this basis, the soil pressure utilization factor, the deformation of the retaining structure and the spatial distribution of internal forces on the cantilever retaining structure in a deep excavation are calculated. Engineering examples show that the foundation pit deformation in considering the spatial effect of soil pressure is consistent with the results measured practically.