Research On The Effect Of Cavities Behind Tunnel Vault To The Stability Of Tunnel Under The Action Of Strong Earthquake

As a kind of common disease of the tunnel lining, the cavities behind the secondary lining would have obvious influence on the stress of the lining. The existing seismic damage investigation records show that the lining of tunnel which around the cavities suffers more serious damage in the process of earthquake ground motion. In view of the situation that a lot of tunnels located in high intensity earthquake region on our country, the research of the stability of tunnel structure deformation and safety with the cavities behind the lining under the action of the ground motion is very necessary.In this dissertation, firstly the influence of the size of cavities on lining structure under the action of earthquake dynamic response is studied using the method of numerical simulation. And then vaults containing cavity under the different earthquake intensity seismic dynamic response of the tunnel are analyzed based on the engineering background of the typical earthquake damage of Long Xi tunnel during the Wen chuan earthquake. Finally optimized analysis of the reinforcement ring parameters is conducted. The main research work and achievements in this paper are as follows:(1) The causes of the cavities and treatment measures are summarized and the causes of the cavities are boiled down to the two main aspect:The construction quality and design reason.The thesis summarizes several common processing measures to cavities behind the lining. Mainly includes back filling grouting, anchor reinforcement, inner surface reinforcement, liner, steel arch reinforcing, the rebuilding of lining.(2) The cavities size on the impact of tunnel lining structure is sfudied and come to the conclusion that the cavities behind the lining vault has obvious effect on the tunnel vault lining structure deformation, internal force and stress. On the whole, with the increase of cavities size, lining deformation is more abvious, bending moment increased and axial force decreases of the cavities location liner, normal stress and shear stress are significantly increased.(3) Based on the factual engineering background, the tunnel structure which contains a wide range of hollow is studied under the condition of different earthquake intensity. The result showed that the earthquake intensity has obvious influence on normal stress sxx, shear stress sxz, axial force and bending moment of lining structure, especially the bending moment which may lead to the lining of large eccentric tensile damage.(4) Optimization analysis of the reinforced region parameters at the cavity for the tunnel is conducted. Come to the conclusion:the stiffness of reinforced region can effectively control the stress of the lining structure and there to be an optimal value, thickness of reinforced region has the corresponding influence on the stress of the lining structure, with the increase of the thickness of the reinforced region, stress of lining decreases, the axial force increases with the decrease of the bending moment, the force of lining is more reasonable.