北江引水工程新型敞开式TBM断层破碎带塌方整治技术研究

Fault and Fracture Zone Collapse Treatment Technology for Open Tunnel Boring Machine Applied in Beijiang Water Diversion Project

为解决以“主机护盾+喷锚支护”为特点的新型敞开式TBM在广州市北江引水工程4#隧洞施工过程中易发生断层破碎带塌方问题,依据断层破碎带地质特点和新型敞开式TBM设备特点,针对性地提出“塌腔化学注浆填充+松散体化学注浆加固+喷锚支护+密布拱架支护+超前注浆加固”塌方整治方案。模拟结果表明:1)断层中心最大拱顶竖向位移约为2.1 mm,拱脚最大收敛位移相对值约为0.05%;2)拱顶喷射混凝土所受最大拉应力约为1.0 MPa,锚杆所受最大拉力约为41.6 kN,均满足受力变形控制要求。在现场实施整治方案后,化学注浆填充饱满,避免了塌腔进一步大范围垮塌对支护结构的冲击;加固注浆松散体胶结效果好,实测形成厚约3 m的承载圈,防止了碎渣的持续滑塌。整治后,围岩初期支护强度得到提高;并对未脱出盾尾的围岩进行预注浆加固,确保TBM顺利通过破碎带。最终监控量测结果表明,最大拱顶竖向位移约为2.0 mm,最大收敛位移相对值约为0.10%,该整治方案有效保障了TBM盾尾后方敞开段的施工安全。

Implementing the innovative"host shield+spray anchor support"open tunnel boring machine(TBM)Guangzhou′s#4 tunnel for the Beijing water diversion project resulted in the collapse of fault and fracture Consequently,considering the collapse characteristics and open TBM,a targeted treatment plan is proposed.This plan involves chemical grouting to fill collapsed cavities,reinforcing loose bodies,spray anchor support,dense arch support,and advance grouting reinforcement.A finite element numerical simulation model is established based on on-site conditions to assess the plan′s feasibility.The simulation results are:(1)The fault center experiences a maximum vertical displacement of approximately 2.1 mm,with a relative convergence displacement of the arch foot of 0.05%.(2)Shotcrete′s maximum tensile stress is approximately 1.0 MPa,and the bolt at the crown has a maximum tensile stress of 41.6 kN,which meets the stress and deformation control requirements.The applied chemical grouting effectively prevents further large-scale collapses of the support structure.Reinforcement grouting successfully cements loose bodies,forming a 3 m-thick bearing ring and preventing continuous collapse of the stone slag.After treatment,the primary support is substantially enhanced.The surrounding rocks not yet detached from the shield tail are pre-grouted and reinforced,ensuring successful TBM passage through the fault and fracture zone.The measured maximum vertical displacement of the arch crown is approximately 2.0 mm,with a relative convergence displacement of approximately 0.10%,ensuring construction safety in the open section behind the TBM shield tail.This approach guarantees structural integrity and safety in challenging fault and fracture zones.