Study On The Evaluation Method Of The Longitudinal Bending Deformation Of The Shield Tunnel In Guangzhou Metro

At present, in domestic subway construction to build the subway shield tunnel occupies a large part of proportion. As more and more metro shield tunnel construction and operation, operation of subway shield tunnel health problem has attracted the attention of a great many experts and scholars. Operation of shield tunnel structure safety evaluation mainly consider lateral deformation and longitudinal deformation of two aspects, for the lateral deformation calculation and performance research there are many, longitudinal deformation research are very few, and lack of safety evaluation index and evaluation method of longitudinal deformation.In this paper, the research on the influence of the lateral elliptical effect on the longitudinal equivalent bending stiffness of the shield tunnel in Guangzhou is considered. Based on the previous to the tunnel longitudinal deformation theory calculation method research based on, according to the parametric equation of ellipse modified longitudinal bending stiffness formula in the position of the neutral axis, and the equation parameters are the position of the neutral axis " c=bsinφ", pushing derived longitudinal transverse effect while taking the of into account to the equivalent bending stiffness calculating formula, and the longitudinal deformation curvature and circular seam opening of the relation between. Thus, a relationship between the crack of ring and longitudinal deformation curvature, but also compensate for the lack of existing research theory of mutual influence between the calculation of transverse and longitudinal deformation of shield tunnel.Secondly, the equivalent longitudinal stiffness ring bolt assumed on the tunnel longitudinal bending stiffness formula of the influence,10 segment 3D fine numerical analysis model was established using MIDAS/GTS, to Guangzhou Metro shield tunnel lining structure parameters to calculate the actual joint and equivalent bolt ring joint to equivalent longitudinal bending stiffness to bring the difference, and the introduction of longitudinal segment ring bolt of equivalent bending stiffness correction coefficient zeta. By calculation, it is known that use actual punctate distribution calculation model of bolt, the bending stiffness compared to equivalent ring bolt, a 10% increase in Guangzhou most shield tunnel stiffness correction coefficient for ζ=1.094, to correct the segment ring bolt equivalent stiffness calculation formula; and according to the Guangzhou Metro 6.0m diameter of shield runnel with segment ring width, bolt type and quantity change relation, combination of equivalent stiffness correction coefficient table, the applicable range of increase the longitudinal equivalent bending stiffness and the opening amount of calculation formula.Then, the circular seam stretching and segment lining structure to joint bolt force. According to the precise numerical calculation model, the analysis of the ring to the joint bolt should stress state, the evaluation of different ring crack opening displacement value and the bolt stress; combination of Guangzhou Metro shield tunnel design standards, construction requirements and ensure the normal operation of the use of functional requirements, the shield the grade standard of longitudinal bending deformation control indexes; synthesizes the research contents, application in Guangzhou Metro shield tunnel longitudinal bending deformation of the safety assessment method.Based on the safety assessment method of longitudinal bending deformation proposed in this paper, the influence of the longitudinal deformation of shield tunnel on the longitudinal deformation of the shield tunnel was evaluated. Taking Guangzhou subway No.2 Line subway tunnel near the foundation pit construction as the engineering background, according to the runnel displacement monitoring data of numerical analysis software MIDAS/GTS established numerical model to verify the rationality of the calculated longitudinal bending deformation curve is obtained, according to the control index and vertical curve obtained girth COD value and by longitudinal deformation control index and the grade standard of evaluation of runnel longitudinal safety performance of proposed suggestions and measures.