Study On Key Technologies Of The High-Speed Railway Tunnel With Shallow Depth And Large Cross Section

ABSTRACT:In the Beijing-Shanghai high-speed railway, the cross-section is large, the amount of tunnels and tunnel-portals are great. The geological conditions of several focus tunnels are extremely complex, which include a variety of adverse geological conditions and special geological conditions. These tunnels are small depth, rock-broken and tunnel-portal bias. Some sections of tunnel are beneath the critical infrastructure of expressway. Therefore the project is difficult in technology. Meanwhile, the project is with high social concern and should not appear the slightest error, as these tunnels are located in East China with developed economy, the ecological environment requires high.To ensure the refinement and safety of the tunnel construction,green engineering and smaller environmental disturbance,this thesis studies the key technologies systematically, with numerical analysis, modeling experiments, field test and engineering application, and the study has taken into account the technique characteristics and environmental requirements of Beijing-Shanghai high-speed railway. Following results are obtained:(1) Researches of advance strengthening technology of shallow, soft rock and large section tunnel.The project researches on a variety of advance strengthening technologies, tunnel surrounding rock deformation and stability taking into account the characteristics of the geological conditions and ecological environment for the Beijing-Shanghai high-speed railway tunnel. Through analysis of the surrounding rock pressure, displacement and the instability pattern during tunnel excavation. The research reveals the mechanism, characteristics, applicable conditions, technical parameters of advance supporting methods to control the surrounding rock deformation. The research has established the basic principles of the selection of advance supporting methods when constructs in the large section tunnel which shallow buried in weak rock. By optimizing advance supporting methods and supporting parameters of tunnel excavation, the safety and high efficiency has been realized in construction of Beijing-Shanghai high-speed railway shallow buried tunnels in soft rock.(2) Researches of key technologies of large section tunnel entrance excavation in adverse geological conditions.Against poor stability characteristics of slop located at entrance of tunnel in soft rock, supporting effects of different pre-reinforced engineering methods are studied in portal section and lithologic boundaries band by means of large-scale similar model, numerical calculation, stability analysis, and field measurement. Reinforcement focus is implemented on each block. The selection principles of the pre-reinforcement methods have been put forward for excavation of tunnel entrance. By optimization of pre-reinforcement methods, Refinement of the design and construction of tunnel entrance are achieved.(3) Researches of tunnel methods of shallow tunnel close under-crossing expressway.Comparisons are made of pressure between the surrounding rock, the primary support and secondary lining, ground surface deformation and blasting vibration of two-step method, two-step method with mid pilot hole, two-step method, two-step method with mid pilot hole, CD method and double sidewall method. Construction methods of shallow tunnel in soft rock under crossing the highway are systematically studied. The pavement largest settlement is 12mm by the obtained optimal construction, blasting vibration velocity has been controlled under 3cm/s. The control principles and methods of construction have been presented and the blasting vibration velocity 3cm/s has been suggested as the vibration control standard when tunneling under-crosses expressway.