盾构出洞冻结法加固土体的稳定性分析

Stability analysis of soil reinforced by ground freezing method for shield launching

运用三维有限差分软件FLAC3D对上海轨道交通某区间隧道盾构出洞冻结法施工过程进行了模拟,对盾构出洞过程中施工稳定性进行评价。施工竖井为地下四层结构,围护结构采用地下连续墙。数值模拟冻结壁水平应力、最大主应力、沿隧道开挖方向位移的变化,将模拟得到的应力与冻结壁强度设计值进行对比,并对隧道轴线方向地表沉降位移进行预测,同时采用安全系数法对施工的安全性进行了评价。安全系数满足设计要求,进一步说明了冻结法在软土地区地下工程施工中的优越性。

This paper introduces the use of finite difference software—FLAC3D to the simulation of tunnel tunneling reinforced by ground freezing method for shield launching,as in the case of a Shanghai tunnel constructed with vertical shaft of underground four-layer structure,and enclosure structure of diaphragm wall.The paper features the numerical simulation of horizontal stress,maximum principal stress of frozen wall,and the changes of displacement with the construction progress,the comparison between the stress value of numerical simulation and strength design value of the frozen wall,and the prediction of the displacement of the ground surface settlement occurring along the tunnel axis,together with evaluation of safety of construction using safety factor method up to the design requirements.This study confirms the advantage of ground freezing method used in the underground construction of soft soil.