软土基坑分区开挖对临近地铁隧道影响的实例分析

Example Analysis of Influence of Soft Soil Foundation Pit Divided Excavation on Adjacent Subway Tunnel

基坑施工对临近既有地铁隧道的扰动影响问题变得越发普遍,研究其影响规律具有较强的现实意义。选取杭州软土地区某临近地铁隧道的超大深基坑工程实例,利用自动化监测及三维激光扫描技术等现场监测手段,获取区间隧道在临近深基坑分区开挖下的变形数据及裂缝发展情况,并结合施工过程对典型断面的监测结果进行分析。研究结果表明:基坑开挖对区间隧道的变形影响呈现出明显的空间效应,可采用分区分层开挖的方式来减小隧道的变形及裂缝的发展;在开挖施工过程中,临近隧道一侧的基坑跨中区域是土层应力释放的重点区域,需要加强监测频次;隧道的裂缝病害与隧道的沉降发展和收敛变形呈正相关关系;三维激光扫描技术可以快速全面地获取隧道管片的变形数据,值得在隧道结构的健康监测和安全评估中推广应用。

The disturbance influence of foundation pit construction on existing subway tunnels becomes more and more common,so it is of great practical significance to study its influence law.Taking a super deep foundation pit project near a subway tunnel in Hangzhou soft soil area as an example,the deformation data and crack development of running tunnel under adjacent excavation of deep foundation pit zones are obtained by means of automatic monitoring and 3-D laser scanning technology.The monitoring results of typical sectios are analyzed in combination with construction process.The results show that the influence of foundation pit excavation on deformation of running tunnel shows obvious spatial effect,and the method of zoning layered excavation can be used to reduce the deformation of tunnel and the development of cracks.In the process of excavation construction,the cross-middle area of the foundation pit near the tunnel side is the key area for the release of soil stress,and the monitoring frequency needs to be strengthened;The tunnel cracks are positively related to the settlement development and convergence deformation of the tunnel.Three-dimensional laser scanning technology can acquire deformation data of tunnel segment quickly and comprehensively,and is worth popularizing and applying in health monitoring and safety assessment of tunnel structure.