Theoretical Study And Test On Mechanic Behavior Of Lining Segment In Shield Tunnel

With the rapid development of economy and the scarcity of land resources of the country, the scale of development and utilization of urban underground space expands year by year. Because of safety, environmental protection and high efficiency, the shield method is widely adopted in the construction of metro. The design of shield tunnel lining is blind because of lack of the standard for shield tunnel, which doesn't take into account the reality of shield engineering in China. In the view of the key problem for design of segmental lining, this dissertation has done the woks about the structure model and key parameters of structure model, which including:1. On the base of the profound comprehension on test of existing segmental lining, a 3D numerical analysis and test using three actual segments were used to analyze the effects of axial force and reinforcement ratio on the failure mechanism and ultimate bearing capacity of segmental lining. The comparison between numerical calculation and test results was made, which shows that the finite element analysis results are in good agreement with the test results. Calculation formulas of the load carrying capacity, crack resistance capacity and crack width for the segment were given, respectively.2. Joint tests using three groups of lining segment were used to analyze joint flexural rigidity and other mechanical properties of lining segment under different conditions.The mechanism of bearing forces and deformations of joint were studied. The quantitative evaluation about joint flexural rigidity and load carrying capacity of lining segment was carried on. On the basis of analyzing the test results, a method to determining the joint flexural rigidity of segmental lining has been proposed.3. On the base of the profound comprehension of numerical analysis of existing segmental lining joint, a 3D finite element model of joint of lining segment was set up. The segments and transmission cushion were meshed by 8-node three-dimensional solid element. The bolts were meshed by 2-node Timoshenko. The comparison between numerical calculation and test results was made. The reliability and reasonability of the finite element model was also certificated。4. On the basis of considering the effects of joint on internal forces and displacements of lining segment, the force method was used to obtain an analytical solution to the internal forces and displacements of lining segment. The influences of joint flexural rigidity, soil resitance coefficient, thickness and calculation radius of lining on the stiffness reduction factor were investigated. A new method to determining the stiffness reduction factor of segmental lining has been proposed.5. On the base of the profound comprehension of design method of segmental lining, the shell-matrix-spring model (SMSM) which can reflect the practical mechanics character of the shield tunnel lining was put forward. In the model, the rectangle plate shell element was used to simulate the segmental lining, the matrix element was used to simulate the longitudinal and circumferential joint effect, the spring element was used to simulate the foundation resistance effect.6. Analysis the mechanics character of segmental lining with the SMSM model and beam-spring model (BSM), compare the mechanics character shield tunnel with segment seams in stagger with variation of joint flexural rigidity, soil resitance coefficient and lining thickness, explain the reason in mechanics that the SMSM results is difference from the BSM.