Study On Optimization Of Construction Scheme And Deformation Law Of Surrounding Rock In Fork Road Sections Of Large-Section Tunnel

China is a large country with rapid development.Its rapid economic growth cannot be separated from the support of smooth traffic.China’s mountainous terrain is relatively complex and special,with hills and plains in the east and plateaus and mountains in the west,so the connection between the east and the west is deeply tied to the development and construction of roads and railways.To improve the traffic network,it is necessary to build a large number of tunnels.For long tunnels,in order to shorten the construction period,it is often necessary to add one or more inclined shafts to improve the construction efficiency of the whole project.When the auxiliary inclined shaft of the tunnel enters the fork of the main tunnel,it is difficult in the actual construction process because of the large excavation section,the complicated surrounding rock stress release and the complicated construction procedure.How to efficiently pass through the fork road construction under the premise of economy,safety and construction quality has become a research difficulty in the field of tunnel engineering.In view of these engineering problems,this paper discusses the construction optimization and surrounding rock stability analysis of large-section tunnel fork section at No.4 inclined shaft fork section of zhengpantai tunnel under the engineering background.The main research contents of this paper are as follows:(1)MIDAS GTS NX 3d numerical simulation software was used to build the fork road model,and the excavation method and the excavation scale of the fork road were compared and optimized.Through the numerical simulation results,the optimization Suggestions of the weak section of the fork road were given and applied to the actual field construction.(2)Numerical software is used to simulate the process of partial excavation,and the displacement variation value of a certain node is analyzed statistically,and the theoretical variation law of surrounding rock deformation is obtained.Then,the deformation law of the surrounding rock of the sankou section is obtained by comparing with the simulated value and the regression value through the processing of the monitoring measurement data in the actual construction process.(3)The field monitoring and measurement data of the optimized scheme were collected,and the measured data were processed and analyzed by exponential function regression in combination with typical sections of the fork road,so as to verify the reasonable applicability of the optimized scheme and provide scientific reference for similar projects.