Research On Mechanical Characteristics And Design Method Of Shallow Tunnel Circular Reinforced By Steel Arch

The problem of lining crack of Beijing subway composite lining tunnel is becoming more and more serious,which brings great hidden trouble to the safe operation of lining structure.However,the time course of "window" on Beijing subway repairing is less than 4 hours,so how to efficiently and quickly under the premise of normal subway operation is an urgent problem to be solved.In this paper,a high strength?light weight and corrosion resistant composite profile tunnel lining structure is proposed.The monitoring data obtained by scanning technique combined with theoretical analysis is used to judge the external load form of the second lining at the present stage.Based on the analysis of elastic shell theory,the mechanical properties of reinforced by composite steel arch are studied,and the approximate analytical solution of horseshoe section is obtained.Based on the quantitative analysis of the damage level of each tunnel disease index,the corresponding strengthening countermeasures are put forward to avoid the problems such as resource waste or bad effect caused by the mismatch between the reinforcement scheme and the disease,so as to provide scientific basis for the optimal design of the reinforced structure.The main work and achievements of this paper are as follows:(1)Based on the structural mechanics method and the convergence deformation monitoring data of the existing tunnel lining,the external load of the lining is analyzed in reverse and the external load distribution function is derived.Then the numerical simulation method was used to simulate the deformation of the model loading external load function,and the numerical simulation results were compared with the monitoring results.The relative errors between the numerical simulation results and the monitoring data in the area near the control point were relatively small,basically less than 20%.The accuracy of the reverse analysis method was verified.(2)To establish the structural mechanics model of the 2d lining tunnel reinforced by composite steel arch,conduct mechanical analysis on the lining tunnel structure reinforced by composite steel arch and its reinforced steel arch and original composite lining based on the theory of structural mechanics and elasticity,establish the differential balance equation and torque balance equation,and establish the internal force calculation formula.On the basis of the two-dimensional mechanical model,the mechanical model of the 3d lining tunnel structure reinforced by composite steel arch is extended to the 3d lining tunnel structure reinforced by composite steel arch.The effect of setting distance and setting stiffness of steel arch on the reinforcement effect is analyzed theoretically.The setting distance and the distance from the center line of the steel arch are the key factors affecting the reinforcement effect.The smaller the distance from the center line of the steel arch,the smaller the convergence residual percentage of the arch and the better the reinforcement effect.When the distance from the center line of the steel arch is greater than b/4,the reinforcement effect of the steel arch tends to decrease rapidly.Therefore,the distance between the center line of the steel arch and the part to be strengthened should be set as less than b/4.(3)Use GTS geotechnical special analysis software and nonlinear FEA analysis software to carry out the numerical simulation research,first of all,according to different steel arch of tunnel reinforced by composite steel arch distance solutions limited analysis simulation,analysis,different reinforcing steel arch rigidity and set spacing is used to numerically simulate the lining reinforced by composite steel arch,under various operating conditions analysis of reinforcement effect as well as the reinforcement of the whole,with Fu Ba Xian engineering examples as the background and theory of the third chapter compared the validation results.The maximum relative error between numerical simulation and theoretical results at the arch waist is less than 15%,and the maximum relative error at the vault is less than 10%,which verifies the accuracy of the theoretical analysis results.(4)To adopt the analytic hierarchy process(AHP)and fuzzy comprehensive evaluation theory and combining with the tunnel operating period monitoring results,to a variety of qualitative description and quantitative expression of damage assessment indicators,through the numerical simulation method to the quantitative determination of index weight,and long-term operation under the condition of the rest of the tunnel lining and quantitatively evaluate the level of damage stiffness.The reinforcement plan corresponding to the damage grade is put forward.The evaluation system is used to evaluate the case of Fubaxian,and the grade is four damage.Based on the theoretical calculation results,the reinforcement scheme of fabricated steel arch is developed for the case of Fubaxian.