Study On Cooling Technology Of Ice Block And Spray In Construction Of Large-section Railway Tunnel

With the rapid development of my country’s transportation field and national strategic needs,railway transportation is gradually extending to complex,difficult and dangerous mountainous areas.More and more long,large and deep tunnel projects will inevitably enter high-temperature areas.The high temperature environment of the tunnel will not only endanger the health of workers and reduce the construction efficiency of mechanical equipment,but also affect the safety of the lining and surrounding rock,restricting the safety,progress and quality of the project.Relying on the Sichuan-Tibet line Layue tunnel project,this paper uses a combination of theoretical analysis and numerical simulation to study the ice and spray cooling technology during the construction of a large-section railway tunnel.The main research contents and conclusions of the thesis are as follows:(1)According to the existing calculation formula,the air volume required for ventilation and cooling during the construction period of the Layue Tunnel was calculated.A numerical model of tunnel ventilation and cooling was established,and the influence of two influencing factors,air supply speed and air temperature,on the temperature field and velocity field of the tunnel was simulated and analyzed.Based on theoretical calculation results and simulation analysis results,the limitations of ventilation cooling are revealed.(2)The simulation calculation of ice cooling in the construction of large-section railway tunnels was carried out,and the influence of ice volume on the temperature of the tunnel face was clarified,and the tunnels were partitioned according to the degree of influence of ice on the longitudinal temperature field of the tunnel.By analyzing the difference in ice melting rate and the influence on the temperature field,comparing the advantages and disadvantages of different ice cube shapes and ice cube placement positions,recommendations for the selection of ice cube cooling schemes are put forward.(3)The simulation calculation of spray cooling in the construction of large-section railway tunnels was carried out,and the movement law of the droplets in the tunnel with the ventilation air flow was obtained,and the law of the influence of the number of nozzles on the temperature field of the upper and lower parts of the tunnel and the position of the nozzles on the droplets were found.The influence law of motion and temperature field,the applicable temperature range of spray cooling and applicable conditions of nozzle placement position are proposed.