Air Temperature Control In Different Operation Periods Based On Qingdao Second Undersea Tunnel And Ventilation Design Parameter Optimization

With the rapid development of China’s transportation industry,the number and length of road tunnels that have been built in China have increased greatly.The geographical conditions along the tunnel are becoming more and more complex,which makes the construction more difficult.At home and abroad,more research is concerned about ventilation smoke evacuation and personnel safety escape during tunnel fires.There is little research on air temperature control on normal driving conditions and blocking conditions during tunnel operation.However,especially in the extra-long tunnels(>3000m),due to cost control,the ventilation shafts are often arranged far apart,resulting in a long ventilation section,which leads to frequent occurrence of high air temperature in the tunnel.Based on the Qingdao Second Undersea Tunnel,this paper establishes a tunnel numerical simulation and theoretical calculation temperature rise prediction model through data collection,collation and analysis.The air temperature in the tunnel under the normal driving conditions and the blocking conditions was predicted in the initial,short and long-term operation of the Qingdao Second Undersea Tunnel.The excessive temperature condition was analyzed under a temperature control standard of 45°C.The temperature rise model was verified by the measured results of winter and summer ventilation effect of Jiaozhou Bay Tunnel.The temperature control measures corresponding to the operation of Qingdao Second Undersea Tunnel under short-term and long-term conditions were given.The main research work carried out and the main conclusions reached are as follows:(1)The numerical simulation and the theoretical calculation of the temperature prediction model of the tunnel are established.In the model establishment,the radiation heat transfer between the motor vehicle surface and the tunnel wall surface is considered.Through the model,the air temperature of Qingdao Second Undersea Tunnel during different operating periods was predicted.The results show that the air temperature in the tunnel is linear.With 45°C as the temperature control standard,under normal driving conditions(vehicle speed 80 km/h),the predicted temperature of the Qingdao Second Undersea Tunnel are not exceeded in the initial,short and long-term operation;under blocking situations(vehicle speed 40 km/h),the air temperature in the initial operation of the tunnel does not exceed the standard,and it has slightly exceeded the standard in the short-term.The air temperature in the long-term has greatly exceeded the standard in each ventilation section.(2)In order to verify the tunnel temperature prediction model,the winter and summer ventilation effects of the Qingdao Jiaozhou Bay tunnel,which has been completed and opened to traffic for nearly 7 years,were measured.The air temperature prediction model was used to calculate the outlet air temperature.The results show that the relative error between calculated temperature rise and measured temperature rise of the left line is within ±15%,and the relative error of the right line is within 30%.(3)According to the prediction result of the air temperature of Qingdao Second Undersea Tunnel,due to the short-term and long-term air temperature exceeding the standard under blocking operating conditions,the temperature control measures of the restricted traffic scheme and the water curtain evaporation cooling scheme are proposed.Because the restricted traffic scheme has a great impact on the tunnel traffic capacity,it is not recommended.When the water curtain evaporation cooling scheme is adopted,the theoretical solution of the outlet temperature in the single-ventilation section using water curtain evaporation cooling is obtained by theoretical derivation,and the method of determining the shortest layout length of the water curtain is determined.The blocking operation conditions were carried out for the detailed calculation and verification of the water curtain scheme.The results show that the total length of the water curtains in the north and south tunnels is 2800 m and 2550 m,respectively,accounting for 18.3% and16.8% of the total length of the tunnel.The tunnel temperature can be guaranteed less than 45°C.(4)In order to explore the influence of ventilation temperature on ventilation volume,based on the actual measurement analysis of the ventilation effect of Qingdao Jiaozhou Bay Tunnel,an optimal design method for tunnel ventilation calculation temperature is proposed.For tunnel ventilation,the outdoor ventilation calculation temperature should be calculated according to the accumulated annual temperature of the outdoor temperature after one hour of the late peak of the traffic flow.Compared with the ventilation calculation temperature according to the current specification,this method reduces the ventilation at the peak of the traffic flow more than 10%,which not only meets the air volume required,but also reduces the ventilation energy consumption.Research results provide reference for the outdoor ventilation calculation temperature of Qingdao Second Undersea Tunnel.