Research On Desing And Construction Technology Of Multi-Arch Tunnel Based On The Single-Hole Method Without Middle Wall

In recent years,with the development of the economy and the improvement of comprehensive national strength,the demand for transportation infrastructure construction in China has gradually increased.Due to the advantages of small floor space,high space utilization,and easy wiring,the multi-arch tunnel has emerged in this era.At present,some multi-arch tunnels have been built in China,and accumulated a certain amount of experience.With the increase of engineering construction requirements for a large number of mountain highways and urban underground traffic complexes,the multi-arch tunnel will have broad application prospects.The main research work and research results are reflected in the following aspects:1.Aiming at the single-hole construction method of the double-arch tunnel without the middle wall,the numerical calculation method was used to compare and analyze the two different process schemes.Then,by considering the structural safety and construction organization comprehensively,the more reasonable construction process is determined.In order to improve the stability of the surrounding rock of the multi-arch tunnel,the treatment measures to expand the reinforcement range between the arches and the construction process of replacing the temporary inverting arch with the cable support are proposed.2.According to the surrounding rock pressure calculation model of separated tunnel with successive excavation of left and right hholes and its related assumptions,the basic characteristics of the single-hole method without middle wall and the load calculation method of the existing code,and the combination of the surrounding rock slip mode obtained by numerical simulation,a load calculation model and method for a multi-arch tunnel without middle wall using the single-hole method is proposed.3.Based on the LS-DYNA dynamic finite element program,the influence of blasting construction on the vibration of the multi-arch tunnel is analyzed.The key parts of the blasting vibration monitoring and the scope of the key protection should be clarified.The longitudinal propagation law of the blasting vibration velocity is obtained.The minimum safety distance between the working face of the back hole and the newly poured secondary lining behind the face is proposed,and a targeted blasting vibration control technology is proposed.4.Through the FLAC 3D program,the structural safety and surrounding rock stability of the multi-arch tunnels with different geological conditions(variation of surrounding rock level and buried depth)and different topographic conditions(ratio of slope,surrounding rock level,and buried depth)were calculated and analyzed.And the geological and topographic applicability of the single hole method without middle wall is clarified.