Study On Deformation And Mechanical Behavior Of Large Section Expansive Red Clay Tunnel Lining

With the rapid development of national railway tunnel construction,the number of long-span tunnels built in China is increasing.Especially in Northwest China,its special topography and geomorphology as well as soil characteristics have brought tremendous challenges to the construction of tunnels.Among them,there is no mature experience to refer to in the construction of high-speed railway tunnel crossing red clay stratum.There is little experience in design and construction,and there is a certain blindness in the construction process.Therefore,based on the project of China Railway Corporation "Research on Tunnel Construction Technology in Loess Source Area of Yinxi High-speed Railway"(2017G007-G),relying on Qingyang Tunnel Project in Gansu Province,taking the surrounding rock of red clay stratum as the research object,and on the basis of experimental research,this paper studies the deep-buried expansive red clay high-speed tunnel with large cross-section by combining indoor test,field monitoring and numerical simulation.Deformation and stress characteristics of surrounding rock and lining.The main research contents are as follows:(1)Through a large number of indoor geotechnical tests,the basic physical and mechanical properties of red clay and its expansion law are studied.The results show that the initial water content has a significant effect on the final expansion rate of soil samples,and there is a good negative exponential relationship between the expansion force and the initial water content.The equation of initial water content and expansion force is fitted.Through direct shear test,the relationship between shear strength and water content of red clay was obtained,and the formula of shear strength of Qingyang red clay was fitted.The effect of different confining pressures on the axial cumulative strain of undisturbed red clay under cyclic dynamic loading was studied by dynamic triaxial test.(2)Based on the laboratory test results of red clay and the field test data of Qingyang Tunnel,the finite element numerical simulation is carried out by using Mohr-Coulomb elastic-plastic constitutive model,and the deformation characteristics of surrounding rock and supporting structure during the construction of retained core soil method for ring excavationof red clay high-speed railway tunnel are analyzed.(3)Combining with the field test of supporting mechanical characteristics of large-section tunnel in red clay,the changing law of mechanical behavior of tunnel lining structure is studied,and the changing characteristics of water content of surrounding rock,stress of steel arch frame and stress of concrete are mastered.Through grasping the information of construction informationization on-site monitoring and timely feedback,optimizing and adjusting the tunnel construction technology and design scheme,it provides a scientific and effective experience basis for the design,construction and risk control of similar projects.