软土深基坑开挖对下卧地铁隧道影响的实测分析

Measurement and analysis of the influence of deep foundation pit excavation in soft soil areas on the underlying subway tunnel

为研究软土地层深基坑开挖对下卧地铁隧道的影响规律,针对某桥梁承台深基坑工程开展下卧地铁隧道在基坑施工期间的变形监测,通过分析隧道累计沉降和水平位移监测数据,研究不同施工工况对地铁隧道位移和变形的影响规律。结果表明:桩基施工引起隧道下沉,基坑开挖引起隧道上浮;隧道变形以0°-180°方向横向变形为主,埋深越浅隧道截面变形越大;最大累计沉降量和水平位移均发生在基坑开挖范围,距离基坑底越近位移越大;软土地区基坑开挖将对下卧隧道产生较大影响,依托工程采取预先加固、超前支护和分层分段开挖的施工方法,能够有效控制下卧隧道的位移和变形。

In order to study the influence of deep foundation pit excavation in soft soil layer on the underlying subway tunnel,for a deep foundation pit project of a bridge cap,the deformation monitoring of the underlying subway tunnel during the construction of the foundation pit was carried out.By analyzing the monitoring data of the accumulated settlement and horizontal displacement of the tunnel,the influence of different construction conditions on the displacement and deformation of the subway tunnel is studied.The results show that:(1)The pile foundation construction causes the tunnel to sink,and the excavation of the foundation pit causes the tunnel to float;(2)The deformation of the tunnel is mainly transverse deformation in the direction of 0°-180°.The shallower the buried depth,the greater the deformation of the tunnel section;(3)The maximum accumulated settlement and horizontal displacement both occur in the excavation range of the foundation pit,the closer the distance to the bottom of the foundation pit,the greater the displacement;(4)The excavation of the foundation pit in soft soil area will have a greater impact on the underlying tunnel.This project relies on the project adopts the construction methods of pre-reinforcement,which can effectively control the displacement and deformation of the underlying tunnel.