北京地铁暗挖隧道变形监测与稳定性数值分析

Deformation Monitoring and Numerical Analysis of Stability for Metro Construction with Mining Method in Beijing

地铁浅埋暗挖隧道施工中,初衬净空收敛量测是初衬结构及周边土体变形最明显的体现。针对北京地铁某浅埋暗挖隧道4种不同工况条件,对4个断面进行不间断收敛量测,结合围岩压力和初衬钢筋内力等多种监测手段,分析二重管无收缩(WSS)全断面注浆和提高初衬强度等施工方法对监测数据的影响。同时采用FLAC3D对暗挖隧道开挖施工进行全过程动态模拟,重点研究隧道开挖引起周边土体位移场的变化情况,进而揭示存在地下水条件下极小净距双洞隧道暗挖施工中4种不同施工方法稳定围岩的效果。结果表明,采用WSS注浆,同时格栅钢架间距500 mm时收敛变形控制在3 mm以内,有利于安全通过风险源和控制隧道变形。

In metro construction with mining method,the most obvious manifestation of initial support structure and surrounding soil deformation is the measurement of initial support＇s clearance convergence.In this paper,the convergence of 4 sections are measured continuously according to the four different working conditions of metro construction with mining method in Beijing subway,combined with methods such as monitoring rock pressure and internal force of reinforcement for initial support,so as to analyze the effect of construction method such as WSS grouting and the method with improving initial support strength on the monitoring data.Meanwhile,the dynamic simulation of the whole excavating process with FLAC3D was established,with the focus on the changes of surrounding soil＇s displacement field caused by tunnel excavation,then to reveal the effect of four different construction methods on the stability of surrounding rock in small interval double-tunnel with groundwater.The results show that using WSS grouting when the space of steel grilles is 500mm,the convergence deformation of surrounding rock can be controlled in range of less than 3mm,which is conducive to passing through the risk source safely and controlling the deformation of tunnel.