盾构隧道下穿顶管通道预保护方案对比研究

Comparative Study of Preprotection Schemes for a Pipe Jacking Channel Over Shield Tunnels

某地下通道顶管工程施工前,根据地下空间规划已知有规划地铁隧道将从下方穿过。为减少后期盾构下穿施工对顶管通道的不利影响,提出了采用旋喷桩门型加固的方法对顶管通道进行预保护。采用有限元软件对不同预保护方案下盾构下穿施工进行数值模拟,分析了不同预保护方案下顶管通道的变形控制效果。模拟结果表明:旋喷桩门型加固对于顶管通道的变形控制效果显著,顶管通道的沉降变形得到了明显控制;双线盾构隧道穿越后,顶管通道的竖向位移曲线呈“W”型,符合类似工程监测规律;门型加固可以有效减少地表沉降,双线隧道穿越后,地表变形最大处居于隧道中心线正上方。采用水平加固体预保护方案地表沉降为无预保护方案地表沉降的80.8%;采用门型加固预保护方案地表沉降为无预保护方案地表沉降的58.5%。

Before the construction of an underground passage pipe jacking project in Hangzhou,it was known that a planned subway tunnel would pass underneath according to the underground space planning.In order to reduce the adverse impact of the shield underpass construction on the pipe jacking channel in the later stage,the method of pre-protection of the pipe jacking channel by using rotary pile portal reinforcement was proposed.The numerical simulation of shield underpass construction under different pre-protection schemes is carried out by finite element software,and the deformation control effect of the roof channel under different pre-protection schemes is analyzed.The simulation results show that:the deformation control effect of rotary pile portal reinforcement on the existing pipe channel is remarkable.The settlement deformation of the pipe channel has been significantly controlled;after the double-line shield tunnel crossing,the vertical displacement curve of the pipe is "W" type,which is in accordance with the monitoring law of similar projects.The portal reinforcement can effectively reduce surface settlement.After the double-lane tunnel crossing,the maximum surface deformation is located directly above the centerline of the tunnel.The surface settlement with horizontal reinforcement pre-protection scheme is 80.8% of that without pre-protection.The surface settlement with the portal reinforcement pre-protection scheme is 58.5% of that without pre-protection.