Study On The Environmental Field Of Bridge-Tunnel Connection In High Altitude Area

The research content of this paper is the extension of the National Natural Science Foundation of China(51778051)—“Research on Wind-Sand Load and Wind Erosion Mechanism of Concrete Structures in Wind-Sand Environment”.With the implementation of the national strategy of speeding up the construction of a powerful transportation country,the infrastructure construction of our country is deepening continuously,especially to solve the construction problems in the central and western high-altitude areas.A large number of tunnels and bridges are built under harsh conditions such as high altitude,severe cold and large temperature difference,and the connection between bridges and tunnels is inevitable.Because the environment inside the tunnel is relatively stable,and the bridge outside the tunnel is in the natural environment,the air temperature and air flow change violently throughout the year,and the surface of the bridge will be affected by solar radiation,which results in the particularity and complexity of the environment of the bridge-tunnel connection section.It increases the difficulty of structural protection.At present,the research on the environmental field of the bridge-tunnel connection is still not perfect,so it is of great significance to study the environmental field(wind field and temperature field)of the bridge-tunnel connection through theoretical analysis and numerical simulation.In this paper,the wind field and temperature field in the connecting section of bridge and tunnel are numerically simulated.The main research contents and conclusions are as follows:(1)The numerical simulation of the wind field in the connecting section of the bridge and tunnel is carried out to analyze the changes of the wind field in different positions and under different incoming wind speeds.Through the analysis,it is concluded that the wind speed in the tunnel is relatively stable,and the wind speed above the bridge outside the tunnel increases,which poses a threat to traffic safety.(2)The numerical simulation of the temperature field in the bridge-tunnel connection section is carried out,and the changes of the temperature field in different positions are analyzed,and the temperature field changes under different wind speeds are analyzed.Through the analysis,it is concluded that under the condition of high temperature,the temperature in the tunnel is lower than that outside the tunnel,on the contrary,it is "warm in winter and cool in summer" under the condition of lowtemperature,and the temperature on the surface of the bridge outside the tunnel is higher because of solar radiation.the temperature change at the transition section of the tunnel entrance is complex.(3)The influence of the train on the wind field and temperature field of the bridge-tunnel connection section is analyzed,and the changes of the wind field and temperature field in different positions under the condition of no car and no car are compared,thus the influence of the train on the environmental field is obtained.Through the analysis,it is concluded that the wind speed at the bottom of the train is higher and the temperature is lower;the wind speed at the top of the train is smaller and the temperature is higher;there is a low speed zone in the leeward area between the train and the bridge,and the temperature in the leeward area is lower than that in the no car condition under the condition of high temperature.on the contrary,it shows that the train and the bridge have the effect of thermal insulation.(4)The coupling effect between temperature field and wind field is analyzed under the condition of the same incoming wind speed and atmospheric temperature.Through the analysis,it is concluded that the wind field is disturbed and the temperature field changes.When the wind speed increases,the heat transfer coefficient increases,the heat transfer performance increases,and the temperature of the surface of the structure and the train decreases.However,under the condition of low temperature,because the temperature of the surrounding rock is relatively constant and higher than the air temperature,the increase of wind speed will enhance the heat transfer performance of the surrounding rock and increase the temperature in the tunnel.(5)Analyze and summarize the research content,and put forward the prospect of related research in the future.