顶管工程工作井位移与土抗力分析

为保证顶管工程的施工安全和经济设计,必须深入分析顶力作用下工作井及周围土体的应力、位移特性.以两个实际顶管工程为工程背景,针对工作井的浅埋、深埋圆形沉井,采用三维有限元分析,给出了浅埋沉井土抗力沿圆周分布的拟合方程.分别采用<规程>1]和<手册>2]推荐的计算方法和三维有限元分析,对顶力作用下深埋、浅埋工作井的位移和新增土抗力进行对比分析,结果表明:①由于只考虑了顶力后背一侧半圆范围内土体抗力的作用,规范法和手册法将导致土抗力计算结果偏大;②顶力作用位置对深埋沉井的井壁变位、土抗力大小和分布情况影响显著;③规范法和手册法仅适用于顶力作用于沉井底部的浅埋沉井.

Analysis of displacement and soil counterforce for working well of pipe jacking engineering

An in-depth study of displacement of working well and soil counterforce under the jacking force is indispensable to ensuring safe and economical construction. Two practical pipe jacking project were employed to represent respectively the deep-buried or shallow-buried circular open caisson which was used as working well of jacking project. Firstly, a fitting equation of soil counterforce distributing around the circumference was obtained by the 3D finite element method (FEM). Then the comparative analysis of displacement and soil counterforce around the working well under the jacking force for both deep-buried and shallow-buried circular open caisson was performed by different method, namely, FEM analysis, specification1] method and manual2] method. The results indicate that: only the soil counterforce that acting at the semicircular was taken into account in specification1]method and manual method; as a result, the calculated soil counterforce are larger than that from FEM analysis. For deep-buried working well, the distribution and quantity of well displacement and soil counterforce are affected evidently by the acting position of jacking force. The methods proposed by specification and manual are applicable only to shallow-buried working well that jacking force acting near its bottom.