杭州市下沙地区某顶管上穿已运营地铁隧道的实例分析

Case study of a pipe jacking passing over an operating subway tunnel in Xiasha District,Hangzhou City

本文以杭州下沙地区电力隧道顶管上穿已运营隧道为例,介绍了顶管上穿时隧道的变形特性及对隧道的保护措施。杭州下沙地区分布深厚的粉砂土,粉砂土具有透水性好、易液化等特点,粉砂土层中顶管施工容易引发漏水事故,同时会引起土体变形进而带动周边隧道变形。顶管上穿隧道时,应采取必要措施加固土体。本文电力隧道顶管与隧道净距2 m,距离较近,上穿位置采用MJS加固,顶管穿越时间应选择在夜间地铁停运时间段,防止可能发生的次生事故影响地铁乘客的生命财产安全。通过三维数值计算分析顶管施工对隧道变形的影响,得到顶管穿越时地铁隧道的沉降变形值,并与实测数据进行了对比分析。结果表明,隧道最大沉降的数值计算值为1.57 mm,实测数据最大值为2.3 mm,顶管上穿时,隧道变形以竖向隆起为主,隧道变形理论计算值与实测值较为接近。本工程采用实时的自动化监测手段,并制定了合理的控制隧道变形的措施,可确保工程安全。

This study focuses on the power tunnel in Xiasha district of Hangzhou as a case study to study the deformation characteristics of the tunnel and the protective measures for the passage of the tunnel with the top pipe passing through the operating tunnel.The area is characterized by abundant silty soil,known for its high permeability and susceptibility to liquefaction.Essential measures should be enacted to strengthen the soil during the passage of the top pipe through the tunnel.There is a 2 m distance between the top pipe of power tunnel and the studied tunnel,indicating a relatively narrow clearance.MJS reinforcement is utilized in the upper crossing segment.The top pipe crossing time should be selected during the night when the subway is shut down to prevent potential secondary accidents from affecting the safety of subway passengers’lives and property.Through three-dimensional numerical calculation and analysis of the impact of pipe jacking construction on tunnel deformation,the settlement deformation of subway tunnels during pipe jacking crossing was obtained and compared with measured data.The results show that the maximum settlement of the tunnel is 1.57 mm by numerical calculation and 2.3 mm by measured data.The clear distance between the top pipe of the power tunnel and the tunnel is 2 m,and the distance is relatively close.The upper crossing position is reinforced with MJS.When the top pipe passes through,the deformation of the tunnel is mainly vertical uplift.The theoretical calculation value of the tunnel deformation control is relatively close to the measured value.This project adopts real-time automated monitoring methods and develops reasonable measures to control tunnel deformation,which can guarantee the safety.