A Study On Mechanical Behaviors Of Shield Tunnel Segment Joint And Structural Residual Capacity Under Fire Scenarios

The study on tunnel fire Prevention engineering is not limited to the smog control and personnel evacuation any more, a number of fire accidents show that the fire may cause severe damages to the tunnel lining structure. Segment joint as a weak link of shield tunnel lining structure, how to evaluate high temperature performance of segment joint correctly is the basis of research on shield tunnel lining structure fire resistance. On the basis of theoretical analysis and numerical simulation, the high temperature mechanical behavior of shield tunnel segment joint and bearing capacity of lining structure are studied, and a series of valuable findings are achieved in this paper:(1) A two-dimensional coupled thermo-mechanical model of segment joint is established to analyze the mechanical behavior of segment joint under high temperature. The law of temperature field, redistribution of internal force and joint deformation are achieved. Besides, the regularity of joint flexural behavior under fire scenarios is discussed and flexural stiffness development with different duration of fires are achieved.(2) Based on analysis of test results about lining materials, the mechanical behavior of high-strength concrete and steel bars subjected to high temperature are achieved. On the basis of lining materials parameters, combined with The ultimate bearing capacity test of segment, the calculation method of ultimate bearing capacity, called simple integral method, conforms with the characteristics of tunnel fire is derived.(3) Based on loading structure method and beam-spring method, and considered with the degradation of strength and stiffness of lining structure due to tunnel fire damage, the calculate mode of the shield tunnel is proposed. In addition, the determination method of fire scenarios are summarized, the calculation method of stiffness on segment and joint are suggested.(4) A calculation procedure to assess structural residual capacity of shield tunnel after fire accident is presented. In this calculation procedure, the load effect is obtained in the way of beam-spring model, the structural resistance is got by the mean of simple integral method, and the security of lining structure is judged with the method of limit bearing capacity envelope diagram.