Complementary ventilation modes of extralong highway tunnel

A ventilation calculation model of complementary ventilation system for highway tunnel was established,its calculation program was designed, and the operation modes of complementary ventilation system for Dabieshan Extralong Highway Tunnel were studied.Fulljet longitudinal ventilation mode,single U-type ventilation mode and double U-type ventilation mode were put forward,and their conversional control conditions were analyzed.The functions of two cross ventilation passages in the tunnel were studied.The pollutant concentrations in the operational state of the tunnel were tested and compared with the result calculated by the model.Analysis result shows that the operation modes of complementary ventilation system for Dabieshan Extralong Highway Tunnel are flexible and practical.When the traffic volume of uphill tunnel is less than 11 500pcu·d-1,full-jet longitudinal ventilation mode is used only.When the traffic volume is within 11 500-14 100pcu·d-1,single U-type ventilation mode is used only.When the traffic volume is within 14 100-18 255pcu·d-1,double U-type ventilation mode is used.The main function of cross ventilation passage near to the entrance of uphill tunnel is to reduce the ventilation volume and speed of uphill tunnel,while the main function of cross ventilation passage away from the entrance of uphill tunnel is to reduce the pollutant concentration of uphill tunnel.When double U-type ventilation mode is used,the ventilation volume of cross passage near the entrance of uphill tunnel reduces,which results in that the energy consumption and operating cost of ventilation system decrease.The absolute values of relative errors between the calculation result and the test result are less than 10%,so the proposed model has high precision and can be applied to the calculation of complementary ventilation.15 tabs,4figs,21 refs.