Shield Tunnel Structure Behavior Under External Load

With the development of the shield technology,shield tunnel has become the main structure in the fields of transportation,hydraulic engineering,municipal engineering,electric power and so on.However,shield tunnels under different circumstances are inevitably affected by the engineering activities in the construction stage or in the service stage.As a structure assembled by the bolts and segments,the tunnel structure safety will be depended on the performance of joints and segments under new construction load.Therefore,the research on the response of joints and segments under external load has a great significance to ensure the safety of tunnel.The effect of external load on the tunnel was more and more cared in recent years.Most of them were simulated as the two-dimensional plane strain structure,or as an equivalent stiffness homogeneous beam,or equivalent homogeneous cylinder.They can not really reflect the response of schield tunnel structure under external load.In general,some developments for response of joints and segments under external load are involved in this dissertation as follows,1.The response of tunnel under vertical lifting construction was analyzed through field monitoring and numerical simulation.The numerical method which simulated vertical lifting construction was proved to be reasonable,based on the comparison between the numerical results and field monitoring results.And the evolvement of the internal stress of segments and joint deformations during different lifting construction phases were figured out.2.The response of tunnel under ground loading was studied by comparing field monitoring and numerical simulation results.A new numerical method which can simulate the response of assembled lining under ground loading was proposed based on the load-structure method.The research was mainly focused on the horizontal convergence and settlement of tunnel.And segment circumferential stress and longitudinal joint deformation were analyzed in detail.3.The response of tunnel under lateral deep excavation was studied.The FEM numerical model which can take segments,circumentional bolts and longitudinal bolts into consideration was proposed.The fitness to calculate the horizontal displacement and horizontal convergence of the model is verified by the field monitoring data.And the most unfavorable position of stress and deformation of tunnel segment and joint were analyzed in detail.4.The waterproof failure mechanism of the elastic gasket at the joint of the tunnel was revealed based on the numerical method.The research was mainly focused on the analysis of the waterproof failure modes of elastic gasket in the open case.