软土基坑施工对临近地铁盾构隧道影响分析

INFLUENCE ANALYSIS ON INTERCITY SUBWAY STRUCTURE AND MUNICIPAL TUNNEL BY CONSTRUCTION OF ATTACHED STRUCTURE

分析基坑施工对临近隧道影响对保护隧道安全有重要意义。对于保护某地块临近地铁盾构隧道,地块地下室与隧道外边缘最小距离约为10.2m,采用有限元方法,建立基坑施工对盾构隧道影响的数值计算模型,分析了盾构管片和轨道结构位移变化特征。研究结果表明,基坑施工过程中,管片和轨道结构位移以向基坑方向的横向水平位移为主,竖向位移和纵向水平位移明显小于横向水平位移;基坑开挖完成后,盾构管片和轨道结构横向水平位移最大值分别为1.494、1.066mm,轨道结构最大差异沉降小于0.455mm,在变形控制允许范围内,并表明盾构管片和轨道结构位移余量足够;基坑第三层开挖是隧道变形控制关键步骤,距离基坑近的左线隧道中心是现场监测的关键位置。

Analyzing the impact of foundation pit construction on adjacent tunnels is of great significance to protect tunnel safety.For the protection of a plot close to the metro shield tunnel,the minimum distance between the basement of the plot and the outer edge of the tunnel is about 10.2 m.The numerical model of the impact of foundation pit construction on the shield tunnel is established by using the finite element method,and the displacement variation characteristics of shield segment and track structure are analyzed.The research conclusions are as follows.In the process of foundation pit construction,the displacement of segment and track structure is mainly the transverse horizontal displacement towards the foundation pit,and the vertical displacement and longitudinal horizontal displacement are obviously less than the transverse horizontal displacement.After the completion of foundation pit excavation,the maximum lateral horizontal displacement of shield segment and track structure is 1.494 mm and1.066 mm respectively,and the maximum differential settlement of track structure is less than 0.455 mm,which indicates that the displacement allowance of shield segment and track structure is sufficient within the allowable range of deformation control.The excavation of the third layer of foundation pit is the key step of tunnel deformation control.The center of the left line tunnel close to the foundation pit is the key position of on-site monitoring.