Research On Mechanical Behavior Of Tunnel Entrance In Seasonally Frozen Zone Based On Ground Temperature Fluctuation

With the rapid development of China’s economy,the transportation industry in China has also developed rapidly.In the seasonal tundra area,a large number of tunnels are being operated and built.The temperature outside the tunnel in the seasonal frozen soil area will change periodically with the change of seasons.In the cold season,the tunnel is prone to freeze damage,while the surrounding rock will melt after the temperature rises.Under the long-term freezing-thawing cycle,the rock mass will be seriously damaged.In order to prevent and control the freezing damage of the tunnel,this paper studies the air temperature field and surrounding rock temperature field in the tunnel in winter,and obtains the change law.The material,thickness and laying method of insulating layer are also studied.The frost-heaving force of surrounding rock is studied by elastic mechanics method.The research results are as follows:(1)according to the engineering example of houanshan tunnel and combining heat transfer and fluid mechanics,the large-scale finite element software ABAQUS is applied to establish three-dimensional tunnel and air model in the tunnel,and the joint simulation of Explicit module and CFD module in ABAQUS is applied to conduct fluid-solid coupling calculation.The reliability of the model and calculation method is verified by comparing the measured data,and the influence of inlet wind speed,wind temperature and tunnel length on the air temperature field in the tunnel and the distribution law are analyzed.(2)Anshan tunnel project as an example,after combined with finite element software ABAQUS to establish the two-dimensional temperature field model of tunnel surrounding rock and initial temperature field model is verified after the reliability and authenticity of the numerical simulation of temperature field of tunnel surrounding rock,explores the distance from the mouth of the cave in the surrounding rock at different distance of the distribution of temperature field and frozen depth.(3)finite element software ABAQUS was applied to study the thermal insulation effect of different insulation materials,thickness and different laying methods on the surrounding rock of the tunnel.The laying effect under different conditions was evaluated,and reasonable insulation materials and laying methods were selected.(4)the influence of freezing depth,lining thickness,lining elastic modulus and frost heave rate on frost heave force was investigated.