Multi-arch Tunnel Under Shallow Buried Bias Of Soft Surrounding Rock Study On Construction Scheme Of Double-side Tunnel Method

With the increasing number of tunnels,due to complex terrain conditions,the phenomenon of tunnel bias caused by different construction methods and construction sequences is common.How to choose the construction method and construction sequence reasonably and reduce the influence of terrain bias on the structural force has become the research direction of many scholars.Based on the proposed Anxiang to Cili Expressway in Hunan Province,this paper uses the finite element analysis program Midas GTS/NX to establish a model of a multi-arch tunnel under shallow buried pressure in weak surrounding rock.Numerical simulation calculation,discussion of the mechanical behavior of the biased double-arch tunnel,and in-depth research combined with on-site monitoring data,the main research contents include the following aspects:(1)Discuss the calculation method of the surrounding rock pressure load of the double-arch tunnel,and study the calculation method of the surrounding rock pressure of the tunnel under the conditions of deep,shallow buried and weak surrounding rock bias.According to the basic theory of numerical simulation,determine the basic data parameters required for numerical simulation in order to meet the actual construction conditions to the greatest extent.(2)Through the analysis and processing of the monitoring and measurement data of Leijiatai Tunnel,combined with the numerical calculation results,the safety evaluation of the supporting structure is provided to provide safety information for the tunnel construction and long-term use.(3)Based on the numerical simulation theory of tunnel dynamic construction,the spatial effects of shallow buried and biased large-section tunnels are simulated and analyzed,including the displacement of surrounding rock,the stress of surrounding rock,the stress of shotcrete,the axial force of the tunnel anchor,and the steel arch Shear axial stress,secondary lining stress,and dynamic stress of the partition wall.Finally,the laws of mechanical behavior of the partition wall and the supporting structure and the reasonable construction sequence were obtained.(4)Designed three types of crossing schemes in line with the site conditions,and established three numerical calculation models for different crossing schemes.The ultra-shallow buried sections of large-biased tunnels were designed according to the unbiased design,the reverse pressure method,and Three traversing schemes with large bias design were simulated and calculated,and the stresses of surrounding rocks and the displacements around the tunnel were compared and analyzed.