Research On Stability Of Surrounding Rock And Lining Strength Of Large Section Highway Tunnel

The road tunnel excavation process is greatly affected by the surrounding rock conditi ons and geological environment,due to economic development,exchanges are getting closer.In order to strengthen the functional complementation between the city and depth of coope ration,more large-section tunnels need to be built.Therefore,it is necessary to study the st ability of surrounding rock and structural optimization of the tunnel to avoid engineering a ccidents such as tunnel cracking and water leakage caused by surrounding rock problems.It is necessary to study the stability of surrounding rock and structural optimization of tunne I.The stability of the surrounding rock of the tunnel is mainly studied from two aspects.T he first is to study the mechanical properties of the surrounding rock of the tunnel,and th e second is to explore the influence of the excavation mode of the tunnel on the stability of the surrounding rock.In the aspect of tunnel excavation and lining,the structural optimiz ation of tunnel can improve the safety and durability of tunnel by selecting reasonable exc avation method and lining support method.The study on the stability of the surrounding roc k and the optimization of the structure of the tunnel is conducive to the reasonable arrange ment of the construction mode,the improvement of the construction efficiency,the accelera tion of the project process,the improvement of the safety and durability of the project,an d the saving of energy.The research object of this thesis is the influence of layered jointe d rock mass on the stability of tunnel surrounding rock and fiber reinforced concrete suppo rt for tunnel lining.The test process of and layered jointed rock mass were simulated by G DEM numerical simulation software coupled with finite element and discrete element.Makin g polypropylene fiber reinforced concrete test block and carbon fiber reinforced concrete te st block.Conduct uniaxial compression test and acoustic emission test to research the role o f fiber reinforced concrete in preventing crack growth.The main work of this paper is as f ollows:(1)calculating the stress variation of the central circular hole in the infinite plane,analy ze each fracture criterion,find out the most suitable fracture criterion for tunnel rock mass.Use polar coordinate system to calculate the displacement around the circular hole and the deformation mode and shape of the circular hole in the plane.Based on the characteristics of this paper,the displacement around the circular hole is calculated by integrating the circ ular hole in polar coordinates.Use Drucker-Prager in the numerical simulation,compared the theoretical analytical solutions and simulation results.It is proved that the circular hole in th e center of an infinite plane will change into an ellipse when subjected to a pair of equal lateral force systems.The strength criteria such as Mohr Coulomb criterion and Hawke Bro wn criterion are studied.(2)GDEM software was used to analyze the mechanical properties of parallel layered jointed rock masses from different angles(0°、30°、45°、60°、75°、90°)and explore the inf luence of the change of the angle between the joint angle and the loading direction on the failure mode of the specimen.Through three loading methods such as static load uniaxial c ompression biaxial compression and pure shear failure forms of such rock mass model at d ifferent inclined angles the stress-strain relationship in the loading process and the variation trend of peak load were analyzed.This study found that the mechanical properties and pe ak strength of the parallel level jointed rock mass were directly related to the joint inclinat ion angle.It was found by simulation that the parallel level jointed rock mass obvious elas tic brittle mechanics under three loading conditions.(3)Studied the characteristics,advantages and disadvantages of different excavation met hods for large cross-section tunnels,the commercial software ANSYS 15.0 is used to simula te the excavation process of two lane tunnel and four lane large section tunnel,and the bir th and death is used in simulating the partial excavation of tunnel,Based on the data of set tlement recorded by monitoring points,compare and analyze the changes of surrounding roc k stress and settlement in each step of tunnel excavation,and explore the influence of exc avation area and excavation mode on surrounding rock stress and settlement.(4)Laboratory test of fiber reinforced concrete,focuses fiber reinforced concrete(FRC)1 ining strength and durability issues in underground conventional infrastructure.Base on mec hanical test,it was verified that the fiber reinforced concrete(FRC)can improve the residu al tensile strength significantly and reduce the crack width in test sample effectively.The s trength and failure mode of different fiber material and content for FRC material by uniaxi al compression and Acoustic Emission(AE)were investigated.Based on the optimal combi nation of lining structure and fiber reinforced material(FRC)property,actual underground engineering as a case study was carried out to verify the feasibility of fiber reinforced con crete in the subway tunnel constructed by the numerical analysis method.Used commercial finite element software ANSYS 15.0 to establish the tunnel lining model according to the engineering example,and simulate the influence of fiber reinforced lining on the stress an d displacement around the tunnel during the process of tunnel excavation.The experimental res ults show that in the process of tunnel excavation,the parts on both sides of the lining are the places with the largest stress,and the vault lining is the places with the largest displacement.The way of fiber reinforced concrete lining can effectively reduce the risk of water seepage and other safety problems ca used by cracks in tunnel lining caused by stress concentration or concrete shrinkage.