基于分层标组沉降监测的基坑工程降水对邻近地铁隧道的影响分析

Analyzing extensometer group monitoring of metro tunnel subsidence affected by adjacent dewatering engineering work

随着轨道交通、高架桥梁、越江隧道等城市交通生命线工程运营规模的不断扩大,重大基础设施地面沉降骨干监测网对保障基础设施安全运营的作用日益突出。本文通过选取典型案例工程,利用现有重大基础设施沿线分层标组的监测成果,开展工程降水活动对邻近地铁隧道影响的分层标组沉降监测分析。分析结果表明,现有分层标组的监测数据能有效反映地铁保护区内基坑降水工程引起软弱土层和承压含水层压缩变形的影响;基坑降水期间地铁隧道的整体沉降趋势与邻近土层的压缩变形趋势相反,而工程降水引发了邻近地铁隧道的差异沉降。

As the scale of urban public transport facilities such as railways,elevated bridges,and river-crossing tunnels expand,monitoring networks for major infrastructure will play an increasingly prominent role in ensuring urban security.This study examines a typical case of a metro tunnel that was affected by an adjacent foundation pit dewatering project.The influence of engineering activities on soft soil adjacent to it and a nearby metro tunnel monitored by an extensometer group was analyzed,and the effectiveness of this monitoring was evaluated.Results showed that the former effectively monitored the deformation of soft soil layers and confined aquifer caused by the foundation pit dewatering.Moreover,although there was some relative settlement of the metro tunnel caused by the adjacent foundation pit dewatering,the absolute tunnel deformation was still controlled by the overall deformation state of the tunnel section affected by the changes in the deep geological environment.