Analysis Of Waterproof Performance Of Sealing Gaskets At Joints Of Subway Shield Segments

Metro shield construction has many advantages,such as fast construction speed,high safety,and little impact on ground traffic.It has become the preferred construction method for metro construction in major cities at home and abroad.However,the leakage problem at the joints of the lining segments of subway shield tunnels has seriously affected the normal operation of subway trains,and has become the primary disease of subway tunnel projects in major cities.At present,domestic and foreign scholars have conducted many studies on the waterproofing of shield subway tunnels.However,the current research mainly focuses on the research on the influence of common factors such as the expansion of the gasket,the amount of misalignment and the hardness of the material on the waterproof performance,and there are few studies on the overall cross-sectional performance of the gasket.Based on the original sealing gasket leakage test results,relying on actual subway projects,this paper adopts the methods of literature data comparison,theoretical analysis and numerical simulation to research on the control indicators of the pros and cons of the gasket cross-sectional form,the influence law of each factor of the gasket cross-sectional form,and the force state of the gasket under the action of water pressure.The main work is summarized as follows:(1)According to the original gasket size and material parameters,the simulation analysis was carried out,and the comparison and analysis with the test data found that:within the allowable joint opening range,the average surface contact pressure can fully characterize the waterproof performance of the gasket.The control index of the overall performance of the gasket: that is,it has a small closing compression force and can release enough surface contact stress to resist the external water pressure after the compression is completed.(2)Based on the above control indexes of the overall performance of the gasket,this paper mainly analyzes the influence of various factors on the comprehensive performance of the gasket,such as the amount of outer profile and stagger,the number of legs,the number of internal cavities,hardness and porosity.(3)By establishing the hydraulic pressure asymptotic permeability model,the method of numerical simulation is used to find the drain water pressure and reproduce the asymptotic leakage process and the final leakage form of the gasket.Relying on a subway actual project,with the help of the aging characteristics of rubber materials,the waterproof performance of the gasket after 100 years of service life is predicted,and the reasonable suggestions to meet the waterproof requirements of the project are given.