Research On Mechanical Performance Of Joint And Control Indexes In Pipe Jacking Power Tunnel

The pipe jacking tunnels using the jacking method are being widely adopted and viewed as a success in engineering practice domestically,as no ground excavation is required and mild disturbance is caused to the surrounding environment during construction.However,in its service state,the pipe jacking tunnel also faces dozens of problems such as excessive longitudinal misalignment or the joint water-mud leakage.One effective way to solve these problems is studying the mechanical performance and failure forms of joints,and determining control indexes for pipe jacking power tunnels.This article focusing on the joint of pipe jacking tunnel studies its mechanical and failure performance.Combined with the research results,the control indexes of the pipe jacking power tunnel during its service state is proposed.The main research contents are summarized as followed:(1)Referring to the longitudinal equivalent continuous model of the shield tunnel,the article simplifies the pipe jacking tunnel: considering the particularity of the jacking joint and using theoretical analysis,the formulas of longitudinal equivalent tensile,compressive and flexural rigidity of the pipe jacking tunnel were derived.(2)In order to make a further exploration of the mechanical and failure forms of the jacking joint,a 1: 1 full-scale test for pipe jacking tunnel joint is fabricated.Firstly,the production procedures of jacked-pipe sections were showed in the dissertation.Then,testing devices were illustrated in detail.Finally,monitoring content and methods were introduced.(3)The test results showed that: the failure process of the pipe could be divided into three stages: the small deformation stage at the beginning of the test,the development stage at the middle stage of the test,and the large deformation stage at the end of the test.The joint was destroyed before the concrete pipe section,and the failure form was disengagement between intrados steel ring and pipe concrete.Then pipe failure was brittle and main cracks penetrated through the pipe wall in longitudinal directions.Combined with the research results,the control restrictions of the pipe jacking power tunnel during its services state was proposed,which could be used for reference in similar engineering.(4)Using Midas/FEA,the finite element numerical model of the full-scale test of the jacking joint was established.This dissertation compared the numerical simulation results with the test,and found out that the two were relatively close.The finite element results could reflect the characteristics of the pipe joint's limit load,deformation,failure shape and other indexes.Simultaneously,the internal force state of the joint was further analyzed.(5)Based on the finite element numerical model,parametric analysis of joint was developed and the results showed: improving the bonding between intrados steel ring and pipe concrete and reinforcement ratio could enhance the capability of anti-deformation and bearing of the joint.However,the improvements are quite limited.