Study On Cross-space Structural Characteristics And Deformation Control Method Of Subway Cross Passage

When two single-line subway tunnels are larger than a certain length,the cross passage should be set up.The cross passage project belongs to the adjacent engineering in the field of subway construction.It is also the most prominent problem in all adjacent engineering.Relying on the construction of a subway cross passage,in-depth research on the influence mechanism of the subway cross-passage construction on the surface and cross-space structure has been conducted,including:based on the random medium theory and superposition principle,the 3D prediction formula of surface settlement due to main tunnels and cross passage construction is derived to calculate the settlement,and the feasibility of the settlement prediction model in the calculation of surface settlement due to cross passage construction is verified.And through three-dimensional numerical model simulation by using FLAC3D,the construction mechanics mechanism is revealed in depth,and on this basis,the sensitivity analysis and optimization of different construction and design parameters are carried out.Then based on the specific engineering,the numerical calculation and mechanism analysis of pre-grouting reinforcement are carried out,and the grouting range and grouting parameters are determined under typical working conditions.The main conclusions are as follows:(1)Based on the mechanism of stratum deformation caused by construction of main tunnels and cross passage,the prediction method for surface deformation caused by multiple constructions with high accuracy is proposed by using the random medium theory and superposition principle.The on-site monitoring data of cross passage is used to verify the accuracy of theoretical prediction.(2)Excavation of the main tunnel causes stress concentration in the surrounding rock near the double-line main tunnel,and an unfavorable form of stress is generated at the opening by the upper and lower parts of the lining.The maximum values of axial force and bending moment are concentrated on both sides of main tunnel spring.Under the combined action of longitudinal and transverse internal forces,the stress on lining structure at the intersection part will become more complex and very unfavorable to the structural safety.(3)The larger the crossing angle between main tunnel and cross passage is,the more favorable crossing structure is.The displacement of main tunnel decreases first and then increases with the increase of clear spacing,and the optimal clear spacing is 10 m.The deformation of main tunnel and cross passage increase with the increase of tunnel depth and show a clear linear relationship.(4)Through effective grouting reinforcement,surface settlement,existing main tunnels settlement and internal forces can be greatly reduced.Under the typical working conditions supported by this thesis,the grouting reinforcement range is 2m and the grouting reinforcement strength is used under working condition 2 can avoid the plastic zone failure of the surrounding rock of the intersection part.