Field Test And Analysis On A7m Shield Segment And Bolt’ Mechanics Characteristic In Shenzhen Metro Engineering Project

ABSTRACT:In the current domestic and even in the world, using the shield to build the subway tunnel is one of the most widespread methods. As the main composition of shield tunnel structure, the shield lining is the most important barrier of standing up to water pressure, earth pressure and some special load. Quality of shield segment lining has a close bearing on the overall quality of the tunnel and safety, but the joint force and connection design of shield lining segments are still relying on the construction experience of stage in the domestic, the study of actual contact force and the connecting bolt stress is relatively small in China. Therefore, the research of shield tunnel segment joint mechanical has become an important topic and the bolts contact force and internal force of shield segment lining seams to the most direct reflection segment, the research is quite urgent.In this paper, carry out the joint of shield segment lining stress and the deformation of joint bolt stress research based on the Shenzhen urban rail transit line11of nanshan-qianhaiwan shield tunnel. The main research content of this paper is as follows:(1) This paper introduces the principle of FBG monitoring technique and the difficulties of fiber Bragg grating sensors embedded in the civil engineering technical. Design a fiber Bragg grating of shield segment joint field monitoring test plan which Cater for the implementation of shield tunnel construction condition by using fiber Bragg grating monitoring technology. Collected the real data of the joint force of shield segment lining and analyzed in practical engineering.(2) Connecting bolts for shield segment joints and field monitoring data analysis, respectively for ring joints, longitudinal seams and toroidal, longitudinal bolt strain change law were analyzed, and using hooke’s law to calculate the stress of the segment joints and connection bolt. Based on numerical simulation method, the finite element software MIDAS, establish simulation of shield segment ring after the actual installation of mechanical model, and the simulation results with the field measured data and theoretical analysis and comparison between the result data connection bolt is consistent.(3) The establishment of a joint force of shield segment lining mechanical model and connecting bolt in the main influence factors of stress deformation mechanics model of shield tunnel segment joint mechanical model gives the joint force and the calculation formula of the stress and strain of the segment. In view of the segment joint connecting bolts, using the method of structural mechanics, respectively connecting bolts is deduced under the segment joint shear force, the wrong units, and under the influence of segment joint open quantity, joint bolt bar the relationship between the size of the moment.(4) By finite element software MIDAS, establishing between the segment and segment through curved three-dimensional model of bolt connection, respectively in the segment of the shear force, fault and joint ctoa three factors, the stress state of the calculation of bolt concluded to bolt the limit tensile stress state, the limit value of the above three factors.