Discussion of Several Problems in Ventilation Design for Highway Tunnel

Whether the ventilation system is designed reasonable or not can significantly affects the construction of long highway tunnel for its high cost in economy and energy.There are several problems in the present Specification for Design of Ventilation and Lighting of Highway Tunnel(JTJ 026.1-1999),such as the calculation of the resistance caused by natural wind in tunnel,the calculation of the amount of fresh air required to dilute smog, and "no circumfluence is permitted in the short section" when ventilating by shaft.On the basis of analyzing and reasoning,the conclusions are reached as the following:(1) The resistance caused by natural wind in tunnel is determined by equivalent pressure difference of the natural wind,and should be assumed to a constant value between 10 and 30 Pa if no observation data is available;(2) When calculating the amount of fresh air required to dilute smog,mass or volume concentration is introduced into the formula to replace the old smog concentration;(3) When ventilating by shaft,it is more reasonable to permit a controllable circumfluence than no circumfluence in the short section.