Research On Seismic Behavior Of Double-layered Lining Structure For Shield Tunnels With Large Cross-section

With the steady progress of railway network construction in China,railway shield tunnels with large cross-section are constructed continuously,and the safety requirements of shield tunnel lining structure are higher and higher.Because the single-layered fabricated segment lining is difficult to meet the requirements of waterproof,anti-seepage and seismic fortification of railway tunnel when crossing rivers and seas,the application of double-layered lining is gradually adopted more and more.However,the understanding of the seismic performance of double-layered lining tunnel at home and abroad is still controversial at home and abroad.It is necessary to carry out research on the seismic performance of double-layered lining of shield tunnels.In this study,the seismic behavior of single and double lining,different connection between segment and secondary lining,and different deformation joint spacing of double lining for shield tunnel under transverse and longitudinal earthquake is invertigated by means of data investigation,indoor test,numerical simulation and theoretical analysis.The main work and research results are as follows:(1)The shear-slip action and interface friction coefficient of segment-surrounding rocks contact surface are obtained through direct shear tests,the shear-slip action of segment-secondary lining contact surface under different connection conditions is obtained,and the interface friction coefficient between segments is aquired.(2)An iterative calculation model that can reflect the shear-slip action of segment-surrounding rock is proposed.The method of simulating the viscous behavior of segment-secondary lining by adhesive contact and suggestions on parameter values are put forward.The effective efficiency of longitudinal stiffness of tunnel under different connection conditions and different deformation joint spacing is analyzed respectively by using three-dimensional discontinuous contact model of tunnel,Based on the stiffness efficiency,the seismic response of different connection conditions and different deformation joint spacing of segment and secondary lining is analyzed by using the Axial Equivalent Stiffness Model.(3)The seismic response difference of single / double lining of shield tunnel is analyzed under transverse earthquake.Compared with single-layered lining,the transverse internal force of double-layered lining tunnel is substantially reduced,the longitudinal internal force is significantly increased,the opening amount of longitudinal joint,the staggering amount of circumferential joint,the relative displacement and transverse bending of tunnel vault and bottom and the damage of segment are reduced.(4)The seismic response difference between the segment and the secondary lining of a double-layered lining tunnel is analyzed considering different connection conditions under lateral seismic action.Compared with the non-friction between layers,the chiseling and planting of reinforcement between layers increase the load-bearing effect of the secondary lining under lateral seismic action,and substantially reduce the opening amount of longitudinal joints,reduce the dislocation amount of circumferential joints,cut down the relative displacement between tunnel vault and bottom,control lateral bending and segment damage,which will increase the damage of the secondary lining and enhance the deformation coordination between the segment and the secondary lining,It is beneficial to improve the seismic performance of the tunnel,and the effect of planting reinforcement between layers is better than that of chiseling.(5)The seismic response difference of double-layered lining tunnel with different deformation joint spacing is analyzed under horizontal and vertical seismic action.The increase of deformation joint spacing will strengthen the internal force distributing effect of the second lining,but will lead to the increase of the longitudinal internal force and the longitudinal bolt stress of the segment and the damage of the segment and the second lining.At the same time,the spacing of deformation joints has little effect on the opening of longitudinal joints,staggering of circumferential joints and the relative displacement of arch crown and bottom,and has a certain beneficial effect on transverse bending.Under longitudinal seismic action,the increase of deformation joint spacing can significantly reduce the opening of segment circumferential joint,especially when the deformation joint spacing is 30 m.