Study On Waterproof Failure Mechanical Of Composite Sealing Gasket For Segment Joints Of Shield Tunnel

With the continuous improvement of urbanization rate in China,urban rapid rail transit,as the most effective mode of transportation,has more and more projects and larger scale.Most of the urban rapid rail transit tunnels are constructed by shield method.When the tunnel passes through soft soil area or underwater stratum,the external side of the shield tunnel bears high water pressure,especially at the segment joint gasket,which causes leakage,is still one of the problems faced by shield tunnel at present.However,at present,the joint gasket of shield tunnel segment usually adopts a single type of gasket.Under the long-term effect,due to the aging of the gasket or the deformation of the joint,the long-term waterproof mechanism of the gasket cannot be realized.At present,there is no research on the joint composite gasket.The waterproof mechanism and optimization of the composite gasket are still blind spot in the research of tunnel waterproof.This thesis performed research work mainly on the following aspects:（1）Research on the mechanism of waterproof performance of composite rubber gaskets.By studying the waterproof model of composite gasket,the finite element model of the composite seal of the shield tunnel segment joint is established,revealing the gasket-seal contact surface and seal under different joint opening and different staggered table.The waterproof performance of the mat-sealing groove contact surface gives the effect of the composite gasket on the waterproof performance of the gasket.（2）Research on optimization of section selection of composite gaskets.The design method of cross-section selection of composite gaskets is proposed.According to the cross-section types of water-expanding rubber blocks of composite gaskets at home and abroad,two types of embedded sections of hexagonal and trapezoidal sections of water-swellable rubber are summarized.Study on the optimization of cross-section selection of composite rubber gaskets.（3）Long-term waterproof performance prediction of composite gaskets.Based on the"PTt"ternary model of the Arrhenius equation.The linear regression fitting is performed by the experimental data obtained by the artificial accelerated aging test,the reasonable aging prediction empirical formula and theσ/σ₀-t stress relaxation parameters of the gasket are obtained,and the aging numerical simulation of the composite gasket is carried out.Finally,the long-term waterproof performance of the composite gasket get a conclution that the mathematical model for predicte.Based on the engineering background of Tianjin Z2 line fast rail transit shield tunnel section,the abaqus finite element software is used to study the waterproof mechanism of the composite seal of shield tunnel segment joints,the optimization of composite gasket section and the composite seal.The long-term waterproof performance prediction of the mat gives the influence of the secondary waterproof effect of the composite gasket on the gasket,the optimized section selection of the composite gasket and the long-term waterproof performance of the gasket and the calculation of the reduction factor for the shield tunnel.Seam waterproofing research and design provides guidance.