Study On The Generation Mechanism Of Crack And Treatment Method Of Shield Tunnel Segment Lining

Urbanization is promoted by the rapid development of national economy in recent years.During this period,the scale of city underground space development has been increasing year by year.The shield method has fast construction speed and high safety performance,has become the main construction method of building the urban underground railway.During the construction and operation period,inevitably there will be many diseases in the shield tunnel,while segment crack is the most common and one of the larger diseases.With the rapid development of shield construction technology,the problem of shield segment cracking has been widely concerned in the field of engineering.In this paper,aiming at the cracking problem in the segment,based on the theory of concrete fracture mechanics,the extended finite element method(XFEM)to study on the shield tunnel under the effect of different load condition,analysis of the cracking mechanism of segment,the main research contents are as follows:(1)Based on the concrete fracture mechanics theory,considering the influence of segment joints to analyze the stress characteristics of the shield tunnel segment,deduced the internal force and displacement of the segment structure.(2)By using the ABAQUS software,using the extended finite element method of tunnel segments cracking simulation respectively to simulation of shield tunnel segment in eccentric load,the cavities behind the segmented lining and relaxation pressure,through a detail comparative analysis from aspects in stress,displacement and crack propagation,the principle of the segment cracking was determined.(3)For shield tunnel has been operating,comparative analysis and complete segment and crack segment at the same loading conditions,the stress and deformation characteristics,analysis of the effect of cracks on the bearing capacity of the whole tunnel structure;for the segment crack,considering the crack depth on its safety The influence of analysis with different depth crack segment in relaxation under pressure,deformation of the cracks,cracks are instability conditions.(4)Through the research and analysis of the cracking mechanism of the shield tunnel,combined with the practical experience of the project,the corresponding measures for the prevention and treatment of the crack are put forward.Standing at the frontier theoretical research,using numerical simulation methods an analysis means,this paper analyzes and studies the mechanical properties and crackingmechanism of shield tunnel segments,provides certain theoretical guidance for the design and construction of shield tunnel,has high engineering application value.