管幕内顶进箱涵前端网格横截面尺寸确定

上海市中环线虹许路北虹路下立交工程是目前世界上在饱和含水软土地层中施工的横截面最大的管幕法工程。为保证在管幕内顶进大断面箱涵(前端嵌固钢板制网格框架)的施工过程中开挖面的稳定性,设计合理的网格横截面尺寸十分重要。根据对网格后端开挖面处的土拱效应分析,采用静力平衡条件与土体的剪切强度条件作为基本控制条件,并结合土体的自稳条件,给出了网格横截面尺寸的合理计算方法,以使网格横截面尺寸设计更加合理,最后以实例说明了具体计算过程。

DESIGN METHOD FOR CROSS-SECTION SIZES OF GRIDS INSERTED IN THE FRONT OF A BOX CULVERT SURROUNDED BY PIPE-ROOF

The subway crossing project through Hongxu Road in Shanghai is the pipe-roof project with the biggest cross-section box culvert up to now in the world.It is constructed in saturated soft soil stratum in the Beihong Road located in the middle ring-road in Shanghai.In order to keep cutting surface stable during pushing the box culvert in the front of which many steel grids are inserted;it is very important to design rational sizes of grids.According to analysis of soil arch effect near the cutting surface of the back end of a grid,rational design approach of cross-section sizes of grids is given on the basis of three important conditions,namely mechanical equilibrium equations,shear intensity principle of soil,and self-stability condition of soil mass.Its concrete calculation procedure is given in detail with the practical project.