Research On Construction Mechanical Behavior Of Urban Tunnel Intersection

With the development of urbanization in our country,land resources on the ground are becoming more and more tense.Under this circumstance,it will inevitably develop underground and develop underground space resources.During the development process,various problems will be encountered.The construction of the intersection of urban tunnels Mechanical behavior is one of the problems often encountered in the development of urban underground space.In the process of tunnel construction,the empty surface of the intersection is larger than that of ordinary tunnels,and the mechanical behavior is more complicated than that of normal tunnel construction.Some theories are still in the stage of summarizing and accumulating experience.This article relies on the Jiefangbei Underground Ring Road Phase III project,through theoretical analysis,numerical simulation,and on-site monitoring,aiming at the intersection area at both the spatial intersection position and the plane intersection position,and the construction process The mechanical behavior is studied.The main research results of this paper are as follows:(1)Using numerical simulation method,the three construction sequences were simulated respectively.When the connecting channel is excavated first,then the power tunnel is excavated,and the main channel is finally excavated,the impact on the surrounding rock stress,surrounding rock and initial support stress of the crossing section is minimal.(2)A three-dimensional numerical simulation was carried out on the excavation process of the main passage,and the stress and displacement of the surrounding rock at the intersection during the excavation of the main passage and the mechanical behavior of the initial support structure were analyzed.The analysis shows that the construction of the main passage destroys the original arching effect of the intersection tunnel.During the construction of the main passage,the surrounding rock stress,displacement and initial support stress of the intersection generally increase.Construction within 15 m on the left and right sides of the main passage will have a greater impact on the surrounding rock and support of the intersection,and the greatest impact on the corner position of the intersection,and the main impact of the construction of the main passage on the surrounding rock of the intersection is about 10 m at the intersection.(3)Using numerical simulation methods,the four construction methods and three kinds of cross-section reinforced support lengths were simulated respectively.When the double-side pilot tunnel method is adopted for the intersection and the single-side pilot tunnel method is adopted for the main passage,the surrounding rock stress,initial support stress,and surrounding rock displacement of the tunnel at the intersection after the excavation of the main passage are minimized.After the initial support of the intersection is strengthened,the load on the surrounding rock will increase accordingly.As the length of the intersection increases,the stress of the surrounding rock at the intersection decreases,the initial support stress increases,and the surrounding rock displacement changes little..When the length of the reinforced support at the intersection is 15 m,the stress of the surrounding rock is reduced the most,and the stress that the initial support can withstand is also the largest.However,from the perspective of safety and economy,it is most appropriate to choose the intersection to strengthen by 10 m.(4)Analyze the site-measured surrounding rock vault settlement and horizontal convergence data,verify the surrounding rock displacement law obtained by the numerical simulation,and use the nonlinear regression method to fit the surrounding rock displacement,and get The fitting function of the surrounding rock displacement of the intersection is compared with the numerical simulation.It is found that the numerical simulation results are in line with the actual project within the allowable range of error.