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.