Model Test Study On The Effect Of High Water Pressure On Lining Structure Of Operating Tunnels In Karst Areas

With the rapid development of China’s transportation industry,the number and mileage of highway tunnel projects are rising,and the tunnel construction technology has also reached a new height.However,at the same time,when complex geological conditions are encountered during tunnel construction and operation,Stability and security are also facing great challenges.The high water pressure behind the tunnel lining in the water-rich karst area is one of the important causes of tunneling diseases,especially in the operation of the tunnel.With the development of karst geology and the poor drainage,strong high water pressure is formed.The damage caused by the tunnel lining will seriously endanger the safe operation of the tunnel.In view of this,this thesis takes Chongqing Tongxi Tunnel as the engineering background,and solves the problems of inrush water and lining cracking damage caused by actual engineering.Through the establishment of tunnel lining calculation model,the function expression of internal force and deformation displacement of lining under external water pressure is derived.At the same time,combined with the hydrogeological parameters of the Tongxi tunnel section in Chongqing,the similarity model test is used to analyze the mechanical characteristics and failure law of the lining under high water pressure,and further research and analysis are carried out on the actual project based on the experimental results using finite element numerical simulation.The main research contents and results are as follows:(1)Based on the load-structure calculation theory,a simplified calculation model of elastic resistance distribution is established.The relationship between the internal force and the displacement of the lining is derived by using the knowledge of structural mechanics,and the displacement caused by the displacement and resistance generated by the compliance coefficient and the external load is established.The function of the function is obtained,and the bending moment function of any section of the lining structure is obtained.Through the deformation function of the bending moment function to any section,the Iterative software is used to perform multiple iterations,and the lining resistance and deformation of the actual engineering local hydraulic pressure are obtained.Displacement distribution law..(2)Based on the similarity theory and dimensional analysis,the similarity constants of similar materials are derived.The similar materials,proportions and physical and mechanical parameters of the surrounding rock and the second lining structure are determined by the physical and mechanical properties of the material.(3)The model test platform was independently developed.The earth pressure loading device and the local water pressure loading device were used to simulate the tunnel surrounding rock pressure and local water pressure respectively.The data collection process and the overall test plan were designed and developed,and the similar model test was used to obtain the variable head.Lining of tunnel lining structure-contact pressure,lining internal force variation law and lining failure mode.(4)Based on the results of model test analysis,a numerical model of similar working conditions is established,and the model test-numerical simulation of internal force distribution curve is obtained,which proves the applicability and reliability of the model test.(5)Based on the basic theory of Midas/GTS plane strain,54 sets of calculation stages were established by using GTS finite element simulation software.Considering the clogging of the lining drainage system,the actual engineering operation tunnels were accepted to withstand different sizes and different load widths at different locations.Under the action of pressure,the force characteristics,deformation displacement and safety coefficient of the tunnel lining structure change.