小尺寸矩形顶管井侧壁反力与变形计算分析

Calculation and Analysis of Side Wall Reaction and Deformation of Small Rectangular Pipe Well

小尺寸顶管井受顶力以及基坑尺寸效应的影响,导致井壁受力复杂,支护结构受力与变形也与传统基坑相差较大。假定靠背侧土体被动土压力的空间分布呈抛物面形,前进侧土体主动土压力按有限土体进行计算,得到允许施加顶力与顶管井侧壁土体反力之间的关系。结合工程实例,借助PLAXIS 3D有限元软件建立小尺寸矩形顶管工作井三维有限元模型,进行顶管施工前后侧壁受力与变形的数值计算。对比分析了小尺寸顶管井各边侧壁受力与变形沿基坑宽度和深度上的分布规律。结果表明,受施加顶力以及空间尺寸效应的影响,顶管井不同侧井壁变形与土压力差异巨大,顶管井平面尺寸对土压力分布也具有明显的影响。分析结果可为市政工程中小尺寸顶管工作井基坑的支护设计优化提供一定的参考。

Due to the influence of the jacking force and the size effect of the foundation pit,the stress on the shaft wall is complicated,and the stress and deformation of the supporting structure are quite different from that of the traditional foundation pit.Assuming that the spatial distribution of the passive soil pressure on the backrest is parabolic,and the active soil pressure on the forward side is calculated according to the finite soil mass,and the relationship between the allowable applied jacking force and the soil reaction on the side wall of the pipe jacking well is obtained.Combined with engineering examples,the three-dimensional finite element model of a small rectangular tube-jacking working well was established with the PLAXIS 3 D.Then the numerical calculation of stress and deformation on the side walls before and after tube-jacking construction was carried out.The distribution of the stress and deformation on the side wall of the small pipe well along the width and depth of the foundation pit were compared and analyzed.The results show that the deformation of the sidewall of the working well and the soil pressure vary greatly influenced by the jacking force and size effect.And the size of working well also has a certain influence on the distribution of soil pressure.The analysis results can provide some references for the support design of small size pipe jacking pit in municipal engineering.