| Southwest China is rich in geothermal resources,and there are more and more high geothermal tunnels in engineering construction.High ground temperature will worsen the construction environment in the tunnel,endanger the health of operators and reduce the operation efficiency of mechanical equipment.Effective measures should be taken to control the temperature in the tunnel during construction.Relying on Xinhua high temperature tunnel of Yumo railway,this thesis studied the comprehensive cooling measures of high temperature tunnel by using the methods of literature research,numerical simulation and field application.The main work and achievements are as follows(1)Based on the basic theory of fluid mechanics,a realizable turbulence model was selected to study the distribution law of velocity flow field and temperature field in the tunnel by using numerical simulation method: the velocity flow field has a significant impact on the distribution of temperature field,and the two develop synchronously to a great extent,which is manifested in that the temperature is lower in the area with high wind speed and higher in the eddy current area with low wind speed.(2)Numerical simulation method was used to analyze the influence factors and laws of high temperature tunnel construction temperature reduction: the side wall ventilation is better than the top ventilation;The distance between the air duct orifice and the tunnel face should be about25m;The ventilation speed is not proportional to the cooling effect,and the cooling effect does not increase significantly when the wind speed increases to a certain value;Compared with placing at the bottom of both sides of the tunnel,ice placed at the axis of the air duct has better cooling effect.(3)In view of the construction difficulties of Xinhua tunnel,such as high external temperature and long ventilation distance in single head tunneling,the change law of tunnel temperature field under ventilation measures,ventilation plus spray measures and ventilation plus ice measures was analyzed through numerical simulation method,and the change law of tunnel temperature field with the construction length of single head tunneling under different construction cooling measures was determined,The maximum mileage satisfying the construction temperature conditions in the tunnel under the three construction cooling measures was0.4km,2.2km and 2.9km respectively.(4)In view of the construction cooling problem in the extra long single heading section of Xinhua tunnel,a comprehensive construction cooling measure of ventilation plus refrigeration and air conditioning was proposed.Further,through numerical simulation and analysis,the reasonable air conditioning and ventilation temperature in the tunnels of different mileage sections was determined. |
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