Study On Numerical Simulation And Cooling Technology Of Construction Ventilation In High-temperature Ground Tunnels

With the rapid development of China's economic construction,the number and quality of tunnel projects have been continuously improved,and the mileage and depth of tunnels are also increasing.The high geothermal energy brought about by the deepening of tunnels and the heat generated during tunnel construction have become one of the main factors affecting the safety of tunnel construction and reducing construction efficiency.During the tunnel construction period,there is only one exit and length restriction for the deep and extra-long tunnels.Natural circulation wind flow cannot form near the face of the tunnel,which results in a serious problem of high temperature and heat damage in the tunnel.Construction ventilation is one of the cost-effective measures to reduce or completely solve the high temperature in the tunnel,and the scientifically designed tunnel construction ventilation system can improve the thermal environment inside the tunnel,improve the construction quality and efficiency of the tunnel,and ensure the safety of the construction personnel in the tunnel.Firstly,the analysis of deep-buried and long tunnels generally adopts the combination of press-in ventilation and tunnel-type ventilation,and briefly introduces press-in ventilation and tunnel-type ventilation and basic characteristics.In order to ensure the convenience of the study,this paper simplifies the process of gas movement in the tunnel to incompressible,non-stable,three-dimensional turbulent flow,and introduces the basic control equations of fluid motion.The characteristics of turbulent flow are described.According to the suitability of the turbulence time-average equation and the k-? twoequation model,the Realizable k-? two equation models are used for turbulence model.Secondly,based on the geological structure and hydrological conditions of the Gaoligongshan tunnel,the formation conditions of the tunnel's high ground temperature were analyzed from the aspects of hydrothermal activity,active faults and magmatic activities.The main heat source was high water temperature and high rock temperature.It provides a theoretical basis for numerical simulation analysis.Taking the deep tunnel with high temperature and long temperature as the research object,the FLUENT module in ANSYS 15.0 was used to analyze the factors influencing the distribution of ventilation temperature field and velocity field in the construction tunnel using numerical simulation method.Select the air supply temperature,air supply speed,and distance from the face of the air duct to three air supply parameters to simulate the ventilation of the tunnel under high temperature conditions.The effects of various factors on the thermal environment inside the tunnel were analyzed under the three different air supply methods: sidewall air supply,dome air supply and central air supply.According to the analysis results,the center air supply method is relatively reasonable.Finally,based on the Gaoligongshan tunnel,according to the results of FLUENT's three-dimensional numerical simulation,the corresponding construction ventilation program,technical measures and ventilation management measures are combined to provide a high-temperature construction ventilation safety control technology to achieve the effect of improving the thermal environment of the tunnel construction.