| The area where Tibet Duoxinla Tunnel is located has strong geological structure and complex geological condition.It is difficult to observe the state of surrounding rock and make timely judgments and control due to its closeness during the process of double shield TBM.As a result,it has a certain impact on construction efficiency and quality.To ensure the smooth progress of construction and optimize the TBM construction process,it is necessary to understand the disturbance law of the surrounding rock during the tunneling process of double shield T BM,analyze the deformation and damage characteristics and give stability evaluation.So this paper starts with the analysis of the three-axis mechanical properties and energy evolution characteristics of rock samples on site.The following research work was carried out for the initial stress field in the tunnel area and the stability of the excavation surrounding rock:(1)In order to analyze the rock mechanics characteristics and the factors of its strength and deformation stability in the tunnel area,uniaxial and triaxial test designs were carried out considering various factors such as sampling location,stress level,stress path,and schistosity characteristics.The specimens made from the rock samples taken from the site were used to make triaxial tests using the MTS rigid tester.Through tests,it is concluded that the gneiss is hard and brittle.Confining pressure and the development status of gneiss ha s a great influence on its strength.Shear parameters of the surrounding rock of the jamming segment are relatively low.The energy evolution law of rock in the process of deformation and failure under different stress paths is discussed based on the energy analysis method,and its energy evolution phase division and destruction mechanism are reached.(2)In order to analyze the in-situ stress field of the Duoxinla tunnel under complex geological conditions,this paper established the 3D geological and rock mechanics model using the elevation information and uniaxial test data of the area,based on the field data collection and analysis.The multivariate linear regression method was used to invert the boundary conditions of the calculation model,and the gro und stress field in this area was obtained.A study was made on the distribution law of the ground stress in the flat section and longitudinal section of the tunnel,and the adverse effect on the stability of the tunnel surrounding rock in different locations was discussed.(3)In order to study the deformation and failure characteristics of tunnel surrounding rock under double shield TBM excavation and its effect on shield extrusion,an energy damage analysis method was proposed based on the triaxial energy evolution characteristics of gneiss.Combining incremental algorithm and plasticity correction method built in FLAC3 D,the energy damage calculation program that can be used for the stability analysis of rock mass engineering is written by FISH language.With this,the 3D numerical value model that can represent the performance of double shield TBM excavation is performed in FLAC3 D.The simulation results show that the main distribution area of the energy damage in the surrounding rock is about 1m away from the tunnel wall.The main damage way should be small rockburst and sheet gang.The increase of tectonic stress and the reduction of rock mass parameters are important causes of the surrounding rock extrusion Shield.Prevention in different situations are recommended.(4)The stress redistribution and deformation law of surrounding rock has spatial effect in the process of TBM excavation.So correct consideration and calculation of this effect can effectively guide the design and implementation of TBM excavation method.This paper used statistical damage constitutive model to fit the constitutive equations of the rock stress-strain curve.Based on the constitutive equation,the elasto-plastic solution of the circular tunnel considering the stress release rate is deduced.By fitting a reasonable longitudinal displacement curve,the analytical solutions of the stress and deformation of the surrounding rock can be obtained under different distances between the tunnel face and the study surface.(5)In order to study the surrounding rock disturbance during the TBM tunneling process of the Duoxiongla tunnel,and to supplement and confirm the deduced dynamic elastoplastic solution of the circular tunnel,this paper prepares the corresponding similar materials for the tunnel rock mass and uses the biaxial test facility to perform.Through tests,the law of deformation of surrounding rock during TBM excavation is obtained,and the stress redistribution law is calculated and analyzed.Through the combination of numerical simulation results and theoretical analysis,the dynamic elasto-plastic theoretical analysis of the circular tunnel is perfected.The disturbance law and deformation characteristics of the cave wall are obtained. |
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