| In order to analyze the characteristics of frost heave mechanics in the end-wall structure of the cold zone tunnel considering the temperature rise and the moisture migration and recharge conditions of the hole,this paper is supported by the National Natural Science Foundation of China(project approval number: 41761015)and a cold area in Qinghai.The tunnel hole section and the end wall type cave door structure are targeted for engineering research.Combined with the thermodynamic correlation characteristics of the frozen soil in the cold region,the finite element analysis model of the tunnel portal section and the end wall portal structure was established by using the finite element calculation software,and the water ice phase transition of the surrounding rock caused by the water condition of the portal was considered.Factors such as temperature rise conditions,analysis of cold zone tunnels.Firstly,the temperature field distribution law near the tunnel portal section and the end wall portal structure is studied.Then,the approximate variation range of the freezing depth is determined according to the temperature field affecting the frost heave force of the end wall portal structure.The analytical formula and numerical simulation are theoretically derived.For the end wall structure,the frost heave force of the end wall structure is determined by considering the temperature rise and the moisture migration and recharge conditions of the hole.The distribution characteristics of the frost-swelling force of the end wall structure are determined,and the indoor similar model test and analysis are carried out.The calculation and numerical calculation are compared to verify the applicability of the proposed method.This paper has done the following work on the main research topics:Firstly,on the basis of reviewing the hydrological and geological data of a large number of tunneling areas to obtain the physical and mechanical parameters of the soil with temperature changes,the boundary temperature function required for thermal analysis is determined according to the site survey results,and then the cold tunnel is frozen.The numerical calculation and analytical calculation of bulging have been elaborated and systematically summarized in the research and development at home and abroad.The initial conditions satisfying the actual engineering conditions to be studied in this paper are proposed,accompanied by phase change temperature field,water field and stress field control differential.The equation and its corresponding three-field coupling implementation process.Secondly,the mathematical model of transient three-dimensional temperature field with phase transition is established,and the temperature field distribution law of surrounding rock and main lining structure near the surrounding rock and lining of the tunnel entrance is studied,and the tunnel section of the tunnel is detected.The temperature distribution law of the axial and radial,the hole door wall structure and the end wall structure near the structure,the approximate variation range of the freezing and thawing circle of the door door wall structure and the freezing depth of the end wall structure in the past 20 years.Thirdly,considering the temperature rise of the tunnel site and the water migration and recharge conditions of the tunnel,the coupled mathematical model of the phase-change temperature field,water field and stress field is used to calculate the hydro-thermal coupling of the end-wall gate structure.The evolution law of frost heave force of the end wall structure and end wall structure of the end wall of the tunnel.Fourthly,on the basis of summarizing the existing frost heaving model,the global frost heave model of the freeze-thaw ring and the concise calculation formula of the frost heave force derived from the elastoplastic mechanics method are respectively applied to the end wall wall and the end wall of the end wall.The structure is analytically analyzed.Fifthly,according to the similarity theory,the indoor similarity model test of the tunnel section of the cold area tunnel is carried out,and the variation law of frost heave force and temperature of the tunnel section of the cold area is studied.Sixthly,the indoor similarity model test,numerical simulation calculation and analytical calculation results are compared and analyzed,and finally the frost heave characteristics of the end wall structure of the cold tunnel are obtained,which provides a reference and ideas for the analysis of the frost heave characteristics of the similar cold area. |
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