MJS工法在盾构上跨隧道工程中的应用研究

Research on the Application of MJS Construction Method in the Project of Shield-driven Metro Tunnels

以南京在建地铁7号线永初路站至雨润路站区间盾构上跨既有2号线油坊桥站至雨润大街站盾构隧道MJS加固工程为研究对象,分别采用数值模拟和现场实测的方法制定合理加固方案,根据实测数据分析MJS桩施工扰动对隧道变形的影响并据此提出工艺参数建议值。研究结果表明:沿既有隧道纵向加固至开挖盾体外侧1.5倍洞径可满足盾构上跨变形控制要求;MJS成桩引起地层应力增大仍会导致隧道发生竖向和水平位移,但不会对横断面收敛产生附加影响。建议软土及粉细砂地层注浆压力不宜大于40 MPa,倒吸水压力应达到注浆压力的50%。该加固方案及盾构超近距上跨工程案例对类似工程的设计和施工具有指导意义。

Taking the MJS reinforcement project of Yongchu Road Station to Yurun Road Station of Nanjing Metro Line 7 crossing the shield tunnel of Youfangqiao Station to Yurundajie Station of Nanjing Metro Line 2 as the research object,the reasonable reinforcement scheme is formulated by numerical simulation and field measurement.According to the measured data,the influence of MJS pile construction disturbance on tunnel deformation is analyzed.The recommended value of process parameters is also proposed.The test results show that reinforcement along the existing tunnel longitudinally to 1.5 times the hole diameter outside the shield body can meet the deformation control requirements of shield upper span.The increase of stratum stress caused by MJS pile formation will lead to vertical and horizontal displacement of tunnel,but it will not have additional influence on the convergence of cross section.It is suggested that the grouting pressure should not be greater than 40 MPa in soft soil and fine sand strata,and the reverse water absorption pressure should reach at least 50% of the grouting pressure.The reinforcement scheme and the case of shield super-close up-span project have guiding significance for the design and construction of similar projects.