管幕预筑隧道衬砌结构现场监测分析

为了考察管幕预筑隧道衬砌结构在土方大开挖过程中的力学响应，对中国首个采用管幕预筑法的工程进行了现场试验，得到了其动态变化规律，积累了现场实测数据，为判断隧道安全稳定提供了参考数据，确保了管幕预筑法的成功应用。研究表明：①衬砌结构的应力和变形均很小，预筑的衬砌结构对于控制结构的变形和地层损失具有很好的效果；②衬砌结构的最大应力监测值仅为强度设计值的30%，预支护结构增强了围岩的自稳能力，并降低了围岩压力；③围岩被动土压力区间较小，衬砌结构与围岩的相互作用不明显；④隧道内部顶层土方贯通当日拱顶沉降达到了5 mm，设计需要考虑贯通过程中的结构和环境效应，施工过程应加强监测与分析；⑤管幕预筑法建造地下空间技术可以有效控制衬砌结构的变形和地表沉降，具有很好的环境效益和社会效益，值得进一步研究和推广。

Monitoring of lining structure of tunnels built by using pipe-roof pre-construction method

The mechanical response of the Chinese first tunnel project built by using the pipe-roof pre-construction method(PPM) during the process of large excavation is studied.The data of dynamic change regulation obtained and the accumulated field measurement can provide evidence to judge the safety and stability of the tunnel and ensure the application of PPM.The study shows:(1) the stress and deformation of the lining structure are very small,the pre-construction lining structure achieves good effectiveness to control the structural deformation and the stratum loss;(2) the greatest monitored value of lining structure is only 30% of the design value of stress,and the pre-construction lining structure improves the self-stabilized ability and reduces the pressure of tunnel surrounding rock;(3) the interval of the passive earth pressure is small,which means the interaction between lining structure and surrounding rock is not obvious;(4) because the settlement at the top of arch reaches 5 mm in the day when the top of the tunnel is penetrated,the structural and environmental effects during the penetration should be considered in the design,and monitoring and analysis need to be intensified during the construction;(5) the PPM technology for building underground space can control deformation in tunnel lining structure and ground settlement,and it has great social and environmental benefits and is worthy to be studied and promoted further.