Numerical Simulations Of Dynamic Construction Process And The Secondary Lining Structure Safety Analysis Of Highway Tunnel

Relying on tangfeng 2 class mingyue mountain tunnel project,the project profile was briefly introduced and the research status of numerical simulations of dynamic construction process and the second lining structure safety analysis of highway tunnel was comprehensively analyzed. Using ANSYS10.0 FEM software, mingyue mountain tunnel's numerical model of shallow period, numerical model of hole body fracture zone and numerical model of load- structure secondary lining structure of tunnel body water-rich section were established. Shallow section of the hole digging were used to CRD-engineering process simulation of tunnel construction,and then the mechanical characteristics of the engineering methods in the tunnel excavation process was analyzed in detail. Body fracture zone of the tunnel was used CD method to simulate the construction process, and then the mechanical characteristics of the engineering methods in the tunnel excavation process was analyzed in detail. Load structure method was used in water-rich section of the hole body, and mechanical properties and safety issues of secondary lining are analyzed in detail with the surrounding rock pressure and external water pressure.Through the CRD numerical simulation method of mingyue mountain tunnel's shallow entrance, the paper presents the main conclusions are as follows: Firstly, mingyue mountain's CRD method adopted in the entrance shallow tunnel is safe and feasible, which can not only apparent control the displacement but also can effectively control the development of plastic zone. Secondly , entrance shallow section surrounding rock stress concentration area of mingyue mountain tunnel mainly appear in a shallow rock around the left and right foot arch , which is also the main plastic zone of the surrounding rock.Through the CD numerical simulation method of mingyue mountain tunnel's deep broken body section, the paper presents the main conclusions are as follows: Firstly, mingyue mountain's CD method adopted in the deep broken body section is safe and feasible, which can control the displacement of vaults, on the other hand, it can control the plastic zone in appropriate depth. Secondly , deep broken body section surrounding rock stress concentration area of mingyue mountain tunnel mainly appear in a 1.5 m depth from cavity surface around left and right foot of the wall , which is also the main plastic zone of the surrounding rock. Thirdly , in the CD method and CRD method, the sprayed concrete axial force of the first guide hole is larger than the subsequent guide hole. Combining the sprayed concrete force characteristics of the two method, the fist supporting of the first guide hole strengthened, while of the subsequent pit weakened.Forthly, whether the CD method and the CRD method succeed or not, the stability of the temporary wall is the most critical factor. the temporary structure of CD method and the CRD method in the subsequent construction process showed a larger internal force. For safety considerations, across the pit during the construction guide, it is recommended for temporary middle wall and temporary Invert for the conduct of the strain monitoring. Through the numerical analysis of the secondary lining structure of mingyue mountain tunnel's rich water body segment, the paper presents the main conclusions are as follows: Firstly ,foot of a wall as well as the invert central section is the weakest cross-section of secondary lining under water pressure. If consider 60% of surrounding rockmass pressure,mingyue mountain tunnel's watch-rich segment secondary lining is up to take the external water pressure of 25m head. If the actual external water pressure is greater than 0.25 MPa, other relevant measures should be taken to ensure the safety of the second lining. Secondly, the second lining structure of axial force increased with external water pressure, the second lining bending changes do not like the axial force that increased with the external water pressure increasing. Individual point bending decrease with the external water pressure increasing instead. Bending moment of vaults, arch shoulder and arch feet changed a little with the external water pressure increasing, while the bending moment of the foot of a wall and invert increased rapidly with the external water pressure increasing. Thirdly ,safety factor of the secondary lining basically decreases with the increase of external water pressure. If you do not take into account the corrosion of concrete and rebar corrosion and other conditions, appropriate external water pressure (about the hight of tunnel) is beneficial to the secondary lining.