Study On Temperature Field In Long Tunnel With High Altitude And Large Slope

As the Belt and the Road initiative continues advancing and the full launch of the Sichuan-Tibet railway projecting and construction in 2018,it is an inevitable trend to build more and more tunnels in high-altitude and severe cold regions.High altitudes and cold regions have low temperatures,and most of them are long tunnels.Therefore,it is more strict to understand the cold and frost insulation technology of long tunnels at high altitude.However,currently available for high-altitude tunnel inside the cave,the temperature field of cold regions,there are many shortcomings and loopholes.The problem of frost damage often occurs,seriously affecting the operation of the high-speed railway tunnel.Grew up to explore high altitude gradient tunnel temperature field distribution,in the domestic 31 has built cold regions tunnel temperature field measured data statistics,and theoretical analysis on temperature field distribution inside,with high altitude cold regions tunnel as the background,the use of fluid heat transfer calculation software ansys fluent for numerical simulation to study the influence of the excess static pressure difference and thermal head on the temperature field of the tunnel in the cold zone,and analyze the influence and distribution law of the temperature field in the high-altitude tunnel.The main tasks completed include:(1)The measured temperature field data of 31 operating tunnels in China,including tunnel length,buried depth,elevation difference between inlet and outlet,geographical location,season,tunnel temperature,wind speed and so on,were analyzed statistically.It is found that the longitudinal temperature field in the tunnel basically presents two kinds of symmetrical distribution and asymmetrical distribution.The characteristics of symmetrical distribution are as follows: in winter,the temperature in the tunnel is high and the temperature at both ends of the cave entrance is low;in summer,the temperature in the tunnel is low and the temperature at both ends of the cave entrance is high,and the buried depth of the tunnel is all below 100 m,and the ground temperature is low.The characteristics of the asymmetrical distribution are as follows: in winter,the longitudinal negative temperature distance of the tunnel with lower elevation is longer than that of the tunnel with higher elevation,the distribution law is similar in summer and winter,and the buried depths are all tunnels above 100 m,and the ground temperature is relatively high.(2)Perform theoretical analysis on the distribution of temperature field in tunnels,through the tunnel aerodynamics and heat transfer theory analysis,what can be concluded is: The difference in elevation between the entrance and exit of the tunnel causes an ultra-net pressure difference;The main reason for the asymmetrical distribution of the longitudinal temperature field in the tunnel in the cold zone is the thermal level difference,which can be caused by the temperature difference inside and outside the tunnel at the entrance and exit.In high altitude zone,tunnels are usually long,large slope and deep buried,so the temperature field in tunnel is often asymmetrical distribution in high altitude zone;Because of the small difference between height inlet and outlet and the small buried depth,the temperature field in the tunnel is distributed symmetrically.Therefore,the influence of the excess pressure difference and the thermal level difference on the longitudinal temperature field in the tunnel is small.(3)Through ansys fluent software to establish 3d tunnel model,and use it for transient calculation,import and export of super static pressure difference,a difference of vertical air and surrounding rock tunnel to simulate the influence of temperature field,velocity field,Drawing out the law of influence on the temperature field of the air and surrounding rock in the cave under different working conditions,and verify the reliability of the numerical simulation through theoretical calculation.(4)Taking the typical high altitude long tunnel along the Xining to Chengdu railway as the engineering background,the air and surrounding rock temperature field and surrounding rock freezing depth of the tunnel along the typical tunnel at different elevations,different ambient temperatures and different buried depths were simulated and calculated considering the thermal potential difference factors,and the high altitude long tunnel was summarized.Distribution law of temperature field of air and surrounding rock in tunnel provides a reference for the cold insulation setting of the long tunnel project at high altitude.