Study On Stability Analysis Method Of Tunnel Face And Advanced Support Design Method Of High-speed Railway Tunnel Constructed By Large Cross-section Method

By the end of 2020,the total mileage of China’s high-speed railway tunnel has reached6003 km,which is far higher than the tunnel construction scale of foreign countries.China has become a worthy of the name of the major country of tunnel.At present,the high-speed railway tunnels in China are mainly constructed by the manual partial excavation method,and this method is difficult to meet the needs of the development of tunnel construction technology in China due to its multiple excavation,large disturbance,low efficiency,and high labor intensity.The large cross-section mechanized method can improve the efficiency of construction,save labor,and improve the quality of project,which is one of the main development directions of the high-speed railway tunnel construction method in China.However,the excavation area of this method is large,and the tunnel face is easy to collapse.Reasonable advanced support measures are the basis for large cross-section mechanized method in soft ground,but there is no reasonable advanced support design method at present.In view of this,the research on the mechanism and design method of tunnel advanced support is conducted in this work,which is of great significance to improve the theory of tunnel advanced support design.The thesis was based on the tunnel projects in Hu Bei section of Zheng Zhou-Wan Zhou high-speed railway,and research methods such as model testing,numerical simulation,theoretical derivation,data research and field test were adapted.The reinforcement mechanism of face bolting,umbrella arch,and face pre-grouting were studied.The mechanical analysis model of the stability of the face reinforced by advanced support was established,and the design method of advanced support was also formed.The main research results are as follows:(1)By the means of model test and numerical simulation,the influence of tunnel advanced support on the development process of failure surface,the failure mode and the stress field of the ground were studied.The reinforcement mechanism of advanced support was analyzed,and the mechanical mode of tunnel face reiforced by advance support was put forward,which provides theoretical support for the establishment of mechanical analysis model.(2)Based on the failure mode of tunnel face,the reinforcement mechanism of advanced support and the mechanical mode of tunnel face,a mechanical analysis model for the stability of tunnel face reinforced by advanced support was established.The formula for calculating the stability coefficient of tunnel face and the limiy support force was derived by using the limit equilibrium method,strength reduction method and elastic foundation beam theory,et al.By comparing with the existing theoretical model,numerical simulation and model test results,the rationality of the mechanical model was verified,which lays a theoretical foundation for the establishment of advanced support design method.(3)Based on the mechanical analysis model of the stability analysis of tunnel face,the flow chart of tunnel advanced support design was put forward,and the design method of tunnel advance support was formed.Based on the tunnel projects of Hubei section of Zheng-Wan High-speed Railway,the advanced support parameters were designed for the tunnel construced by the large cross-section mechanized method.The rationality of the advanced support parameters and the reliability of the design method were verified through engineering application and field tests.