Research On The Mechanical Performance Of The Circumferential Mortise And Tenon Joints In Prefabricated Frame Tunnels

Under the "dual carbon" goal,prefabricated tunnels have gradually become an important direction with the development of tunnel engineering due to their advantages in energy conservation and environmental protection,and have been widely applied.However,there are some problems when using prefabricated tunnels.The stiffness of the lining joints of prefabricated tunnels is lower than that of other parts of the lining,and the force transmission mode of the joints also exhibits nonlinear characteristics,resulting in weak mechanical performance and complex mechanical mechanisms.Compared with other parts,prefabricated tunnels are more prone to diseases such as cracks,deformation,and leakage,which has attracted widespread attention from researchers.Prefabricated frame tunnel is a type of prefabricated tunnel,which also has the above problems in practical application.However,there is currently a lack of research on the design and mechanical performance of the circumferential mortise and tenon joints in prefabricated frame tunnels,especially the corresponding full-scale tests,which are not conducive to the development and application of this type of tunnel.Therefore,conducting research on the design and bending resistance of circumferential mortise and tenon joints is of great significance for improving the safety performance of prefabricated frame tunnels.This article explores the mechanical performance of the circumferential mortise and tenon joints in prefabricated frame tunnels,relies on the projects such as the National Natural Science Foundation of China(52208388),and based on methods such as data analysis,full-scale experiments,theoretical research,and numerical simulation.The main research content is as follows:(1)Through the analysis and research of prefabricated tunnel lining joints at home and abroad,a new type of circumferential staggered tenon joint structure was designed,and full-scale model tests of the joints were conducted.The research results indicate that the load deflection curve of the joint exhibits significant three-stage changes throughout the entire loading process,and exhibits a linear variation characteristic.The cylindrical joint is closed earlier under pressure,and the initial neutral layer is lower.The presence of steel columns prevents significant deformation of the joints and enhances their bending resistance.(2)Based on the experimental data of the full-scale joint model,the stress mechanism of cylindrical and square column joints was analyzed,and their stress performance under static load was explored.The research results indicate that both cylindrical and square column joints exhibit progressive failure behavior,with the deflection ductility index and rotational ductility index of cylindrical joints being 2.28 and 1.98 times higher than those of square column joints,respectively.The stiffness and load-bearing capacity of cylindrical joints are weaker,but the rotation angle and load increment at each stage are smaller at the same load level,exhibiting higher ductility.The cylindrical joint exhibits a tensile bending failure mode,while the square column joint exhibits a compressive bending failure mode.(3)A refined numerical model was established using numerical simulation software to simulate the mechanical behavior of the joint under different parameters.The research results indicate that the bearing capacity of the joint increases with the increase of preload,but the number,width,and damage area of the joint cracks increase with the increase of preload.An increase in the size of steel columns is beneficial for the synergistic stress between steel columns and concrete.The downward movement of steel columns on the surface can not only limit joint deformation,but also improve the load-bearing capacity of mortise and tenon joints.