Research On The Control Method And Application Of The Interaction Between Two-line Shield Tunnels With Close Spacing

With the expansion of the scale of cities and the gathering of population,urban traffic is increasingly extending to the underground space,and the volume of urban underground tunnel construction will become more and more huge in the next few years.However,urban underground space resources are very limited,and there are a large number of building foundations,underground pipe networks and other structures in the underground space.It is impossible to guarantee that all tunnel lines have enough underground space,especially in dense central urban areas and old urban areas.The distance between the left and right lines of the double-lane tunnel is too small to meet the requirements of the standard design.In this case,the shield construction of the subsequent tunnel will cause deformation and displacement of the preceding tunnel,reduce structural safety,increase leakage risk,affect the normal use of the tunnel,and bring greater safety to the construction and operation of the tunnel Hidden dangers.Based on this,this paper mainly studies the mutual influence and control measures between tunnels for the close-spaced double-line shield tunnel project,hoping to provide theoretical guidance and reference for similar projects,and improve the safety,reliability and economy of construction.The main research contents and results are as follows.(1)Through reading related literature,systematically analyze the mechanism,law and harm of the mutual influence between two-line shield tunnels with close spacing.On this basis,corresponding control measures are proposed from the three aspects of "weakening the disturbance-reducing the transmission-strengthening the protection object",and analyze the applicability of each control measure.(2)Taking the subway tunnel project of Line 7 in a certain city as a case,combined with the actual engineering situation,corresponding control measures are formulated to reduce the mutual influence between the tunnels.Establish an ABAQUS finite element model,summarize the key steps and implementation methods of shield tunnel engineering modeling,compare the numerical simulation results with the engineering measured data,and verify the reliability of the mechanism analysis and modeling method.Through quantitative analysis,it’s found that the protective effect of isolation piles is mainly reflected in three aspects: reducing surface settlement,reducing the stress of the preceding tunnel,and reducing the overall displacement of the preceding tunnel.(3)Introduce the method of orthogonal experiment to optimize the design of the isolation pile parameters in the example.Based on the ABAQUS finite element model,design the orthogonal experiment scheme,and conduct intuitive analysis and variance analysis of the test results.The analysis shows that: The pile length in the range of 23-43 m and the pile diameter in the range of 0.4-0.8 m will significantly affect the isolation effect of the isolation pile,while the pile spacing in the range of 0.6-1 m has a small effect on the isolation effect.Based on this,an optimization plan is proposed: The distance between the piles in the actual project is expanded from 0.8 m to 1 m,and numerical simulations prove that the optimized isolation piles can still exert a good isolation effect,and the project cost has been reduced by 20%.