Stress Analysis And Durability Study Of The Segment Structure Of Xiangjiang Shield Tunnel In Hengyang

With the development of the society and the progress of the economy,the demand for the tunnel is becoming more and more large in every city.In the underground tunnel construction,shield as a safe,economic and rapid construction method of tunnel has been widely used for shield tunnel lining segment,the shield segment is the skeleton of the tunnel,safety performance of the segment structure have important influence on the tunnel engineering.During construction process,segment structure not only bear the pressure of the surrounding formation,but also need to take the jack thrust and the gradual variation of the grouting pressure,the external load changes above factors will have a certain impact on the segment and segment joint;shield tube sheet in corrosive environment,the service life of the structure under the current form can meet the requirements of design for 100 years.Therefore,the stress characteristics of the shield segment structure and lining durability,has attracted more and more attention of engineers;based on the background of Hengyang City,two sets of Xiangjiang Hejiang loop shield tunnel,the stress on the segment of properties and durability,the main contents and results are as follows:(1)after reading and collecting the research results of shield tunnel at home and abroad,this paper introduces the research status of shield tunnel at home and abroad,the general situation of tunnel engineering and the scheme of detection,and summarizes the calculation method of shield tunnel design,the calculation model of shield segment and the calculation method of load.(2)modeling with ANSYS finite element software to study the mechanical properties of segment lining under construction load,and compare different angle of assembly,thrust force and grouting pressure.The horizontal displacement and vertical displacement of the segment decrease with the increase of the angle of the wrong joints,but the displacement is the smallest when the dislocation angle is 20 degrees.With the increase of Jack thrust,the horizontal and vertical displacement of the segment decreases,but it is not obvious.When Jack thrust is 4000 kN,the displacement and settlement are minimum.With the increase of grouting pressure,the vertical displacement of the segment decreases first and then increases.When the grouting pressure is 0.2-0.3MPa,the vertical displacement is the smallest and the horizontal displacement of the segment decreases.When the grouting pressure is 0.4MP,the horizontal displacement is the smallest.(3)the special working environment of shield tunnel concrete segment is analyzed,and the main factors of its durability are concrete carbonization and chloride ion erosion.Through the analysis of the influence factors of durability,the durability life of the tube structure is predicted,which is in line with the design requirements.The anticorrosion measures of the segment of the shield tunnel are also discussed.