The Structural Safety Evaluation Of Disease Tunnel Based On Finite Element Method

Tunnel is a underground structure of artificial excavation in the national formation, dueto the impact of construction, materials and changes of geological environment. The tunnel ofexisting lines inevitably produce a variety of tunnel disease during the operational phase.Structural disease is the most particularly significant impact for safety and reliability of tunnellining in all kinds of tunnel disease.This paper is based on survey and detected of Pingxingguan tunnel that is located in theJingyuan railway line, combined with the design construction and final acceptance of thetunnel, using the finite element method of numerical simulation, mainly studied the impact ofthe tunnel lining security that caused by tunnel lining cracks and cavities behind tunnel lining,achieved some conclusions that can be used as the theoretical basis of the treatment of tunneldiseases.This paper carried the following research works and achieved certain conclusions:(1) By investigated and detected the field disease, to obtain the disease status of tunnellining cracks and Cavities behind tunnel lining of the Pingxingguan tunnel, that provided theparameters of calculate required for further finite element simulation.(2) This paper have used finite element numerical analysis method, used contactelements to simulate the tunnel lining cracks, analyzed impact of tunnel lining safety thatcaused by the same depth of cracks in different locations of the tunnel and the different deepof cracks in the location of the tunnel arch. It used Griffith criteria to determine the security ofthe tunnel lining structure that existed cracks.(3) This paper have used ANSYS finite element software to establish the calculated model withcracks in the lining structure and to solve the nodal displacements near the crack tip. In order toobtain the stress intensity factor near the area of crack tip, for judging the security of the liningstructure with crack.(4) This paper have used finite element numerical analysis method, simulated the tunneldisease of cavities behind tunnel lining, by the comparative analysis of without cavitiesbehind lining, found different effect of tunnel lining structure security that caused by differentsize cavities in the same location of the tunnel lining behind and same size cavities in thedifferent location of the tunnel lining behind. It used safety factor of lining structural todetermine the lining structure security of cavities behind lining disease. (5) Impact caused by cracks depth on the safety of the tunnel lining is very significant bymeans of numerical simulation analysis. The cracks parts of lining structural reached the state ofcriticality safety, if the cracks depth came to1/4of the thickness of lining. Cracking site of liningstructural have full turned into the plastic state, if the cracks depth came to3/4of thethickness of lining.The scale of cavities behind lining have a greater impact on the security of tunnelstructure. The lining structure of existing cavity will have a greater moment than that withoutcavity and generate a large tensile stress at the bending moment tension side. Cavities behind liningis extremely detrimental to the security of the tunnel lining. Also, the result has verified thatthe closed state of structure lining and surrounding rock is very useful for tunnel structure.The results of this research and the methods can be used to provide information andreference for similar tunnel disease remediation work in the future.