Research On Comprehensive Temperature Control Technology During Construction Of High Ground Temperature Tunnel

With the development of our country’s economic construction and the progress of highway construction technology,there are still many highway projects in progress on the land of China.It is inevitable that many tunnel construction problems will inevitably be encountered during highway construction.High ground temperature tunnels are a type of tunnel that needs special attention among many types of tunnels.Carry out research on the comprehensive temperature control technology of high ground temperature tunnels,study the numerical simulation effect of ventilation and cooling on the face of high ground temperature tunnels,propose ventilation cooling technology to improve the ventilation effect of high ground temperature tunnels,and design the ventilation and cooling system of high ground temperature tunnels.It is of great significance to ensure the safe construction of high ground temperature tunnels,create a civilized tunnel construction environment,and protect the health of construction personnel.This article is based on the actual high ground temperature tunnel project.The author first investigates the construction site,combined with the geological survey and ground temperature report,the author analyzes the formation conditions and causes of the high ground temperature of the tunnel,and conducts temperature measurements on site to provide numerical simulation for ventilation and cooling.The necessary preparations were made;then the author used FLUENT numerical software to simulate the construction ventilation process,and summarized the influence of the two parameter changes of the tunnel ventilation system’s air duct inlet temperature and inlet wind speed on the cooling effect near the tunnel face;at the same time,the author is based on the numerical simulation The method optimizes the thermal insulation layer laying plan,guides the selection of materials and parameters of the high ground temperature tunnel on-site insulation layer,and finally determines the optimal thermal insulation layer laying plan.The main research results obtained in this paper are as follows:(1)Combining the geological report of Nige Tunnel and the regional literature data of Yunnan Province,the author concludes that the lithology of Nige Tunnel site is Yanshanian period granite(γ53(a)),and its magmatic activity formed earlier,so Nige Tunnel is high.The heat source of ground temperature is less likely to come from the heat source of magmatic rock activity.(2)Nige Hot Spring,Laohutan Hot Spring,and Yashadi Hot Spring are distributed around the entrance and exit of Nige Tunnel.The high ground temperature of Nige Tunnel is the same as the hot spring heat source.The hot springs are the discharge outlets of the geothermal heat source and connect to the underground heat source.The hot spring water heat source around Nige Tunnel comes from the deep region of the earth’s crust,carries various chemical constituents in the form of hydrothermal or steam(mainly characterized by the accumulation of sulfur-containing substances),and passes through various channels(faults,fissures,etc.)Conducting shallow sections to form tunnel geothermal or hot springs.(3)Based on the FLUENT numerical simulation software,the author performs ventilation and cooling numerical calculations for 8 simulated working conditions.According to the calculation results,increasing the wind speed at the inlet of the air duct within a certain range can quickly balance the temperature in the tunnel and improve the cooling effect,but it exceeds after a certain value,increasing the wind speed at the inlet of the air duct has less and less influence on the cooling of the tunnel;when the wind speed at the inlet of the air duct is the same,the lower the air temperature at the inlet of the air duct,the better the cooling effect in the tunnel.(4)Considering the maintenance of the high ground temperature tunnel during the operation period and the prevention of high heat damage in the tunnel,it is very necessary to lay the heat insulation layer in the high ground temperature tunnel.According to the factors affecting the temperature in the tunnel,the orthogonal test is designed and the numerical simulation of the heat insulation layer scheme is carried out.According to the numerical calculation results,the temperature of the tunnel decreases from the outer layer to the inner layer of the tunnel.The average temperature of the surrounding rock area is the highest,followed by the primary lining area,the waterproof board area,the insulation layer area,the second lining area,and the tunnel area.The temperature difference between the outer zone of the thermal layer and the inner zone of the thermal insulation layer is obvious,indicating that the thermal insulation layer has a very significant effect on the second lining of the high ground temperature tunnel and the temperature reduction in the tunnel.(5)According to the numerical calculation results of the orthogonal experiment,the wind speed in the tunnel has the greatest influence on the temperature in the tunnel area,followed by the surrounding rock temperature,the thermal conductivity coefficient of the insulating layer material,and the thickness of the insulating layer on the temperature in the tunnel area.The degree is the smallest among the four factors.The optimal level of each factor is: tunnel wind speed is 7 m/s,insulation layer material temperature conductivity coefficient is 0.02w/m·k,layer surrounding rock temperature is 55℃,insulation layer thickness is 9 cm.