Study On Ground Anti-Freezing Of Tunnel Entrance In Cold Region

Mine tunnel is an important channel for mine safety ventilation and ore material transportation.In cold regions of China,the ambient temperature in winter is low,and the extreme temperature can reach below-30℃.Therefore,when the calculated temperature outside the heating room is below-5℃and the ground is flooded,the ground at the entrance of the mine tunnel needs to be treated with anti-icing.On the basis of referring to relevant literatures and theories,this paper puts forward the ground anti-freezing method of laying buried heat pipe on the ground in the low-temperature area of caiaying zinc gold mine entrance section in Zhangbei area.Using ANSYS software to simulate the different environmental temperature,hot air from the mine ground height,hot air supply Angle variable temperate rock and soil layer under the condition of regional tunnel entrance section of the temperature of the hot and cold wind mixing flow field,the analysis of the mixing flow uniformity and the change of the surface air temperature area,to determine the mine ground area buried heat pipe buried pipe at low temperature range,At the same time,the surface heat dissipation,constant temperature rock layer and environmental cold air affecting the mixing of hot and cold air are compared and analyzed.On this basis,a series of researches are carried out on the temperature field of the mixed air flow of cold and hot in the tunnel with different buried pipe depths and the mechanical characteristics of the buried heat pipe under the static load on the ground,as well as the temperature field of the mixed air flow of cold and hot in the tunnel with different diameter and spacing of the single pipe.The research contents and conclusions of this paper are as follows:1)With the decrease of ambient temperature,the range of low temperature area in the tunnel increases and the uniformity of mixed air becomes worse.The existence of local low temperature area on the ground of the entrance section of the tunnel is mainly caused by the uneven mixing of cold and hot air in the entrance section of the tunnel.The higher the height of hot air opening from the tunnel ground is,the worse the mixing uniformity of cold and hot air in the tunnel is and the larger the low temperature area near the ground is.When the hot air outlet is 0.2m away from the tunnel ground,the anti-freezing effect of the tunnel entrance section ground is the best.The smaller the hot air supply Angle is,the more uniform the mixture of hot and cold air is,and the smaller the low temperature area near the surface of the tunnel is.When the air supply Angle of hot air is 0°,the ground anti-freezing effect of tunnel entrance section is the best.2)By analyzing the temperature field of the mixed hot and cold air in the tunnel entrance section before and after the optimization of different ambient temperatures,the tunnel surface area 24 m away from the tunnel entrance is taken as the laying range of buried heat pipe.Through the comparative analysis of the influencing factors on the mixing of hot and cold air in the tunnel in the rock and soil area with variable temperature layer,it is found that the surface heat dissipation and constant temperature rock and soil layer have little influence on the mixing of hot and cold air in the tunnel,and the main influencing factor is the environmental cold air.3)With the increase of buried pipe depth,the additional pressure of ground load decreases gradually,but the pressure of back packing increases gradually,and the temperature of near-ground air flow just above the center of pipe top decreases gradually.When the depth of the buried heat pipe is 100 mm,the ground anti-freezing effect of the tunnel entrance section is the best.With the increase of pipe diameter,the thermal influence area gradually expands,and the near surface air temperature just above the center of the pipe top gradually increases.When the diameter of the buried heat pipe is DN125 mm,the ground anti-freezing effect of the entrance section is the best.With the increase of pipe spacing,the thermal disturbance between pipes and the temperature of near-earth air flow directly above the center of pipes decrease gradually,and the thermal influence area increases gradually.When the distance between buried geothermal pipes is 200 mm,the ground anti-freezing effect is the best.The research results of this paper provide a certain theoretical basis for the design and construction of tunnel ground anti-freezing,and provide reference for further research.