Study on problems of the air exchange time for highway tunnel

The calculation of air volume demanded in long highway tunnel has an important impact on the choice of ventilation scheme and working costs of tunnel.There are several fuzzy provisions in the present Specification for Design of Ventilation and Lighting of Highway Tunnel(JTJ 026.1-1999).Combined with the ventilation design process of Baojiashan extra-long highway tunnel,these issues were analyzed and argued.Based on the economic point of ventilation,the current air exchange time in highway tunnel is too high.Therefore,the air volume under the air exchange condition is much higher than that under the other conditions.As a result,the air volume under the air exchange condition becomes the main air volume in tunnel ventilation,and this phenomenon is more obvious in the last ventilation of tunnel.The qualitative theoretical analysis shows that the air exchange time is a variable function of tunnel multi factors.