高地温小断面隧道施工通风排污降温效果研究

Study on the Effect of Blowdown and Cooling of Ventilation in Construction of Small Section Tunnel with High Ground Temperature

为评估高地温隧道施工拱顶送风效果,以成昆铁路米攀段保安营1号隧道为依托,采用数值模拟方法建立围岩-衬砌-洞内系统掌子面模型,研究不同送风速度和温度下施工通风排污降温时效,得到隧道施工通风期间洞内CO浓度和温度分布时空变化规律:(1)在通风温度15℃下,距掌子面100 m范围内爆破产生的CO清空时间随风速增加而减少,15 m/s风速仅需约350 s, 10 m/s风速需要约550 s,而5 m/s风速需要通风30 min,难以满足施工排烟需要;(2)在通风温度15℃下,大于等于5 m/s风速均能使隧道内气温下降至施工需求,且10.5 m/s和15 m/s风速其降温效果相当,而5 m/s风速降温效果较差;(3)在设计通风风速9.61 m/s下,距掌子面200 m范围内隧道气温下降用时随风温增加而增加,15℃和20℃风温分别用时约为160 s和170 s,而25℃风温只能使距掌子面150 m范围内的气温满足规范要求。

In order to evaluate the effect of air supply in the arch roof of tunnel construction with high ground temperature,a tunnel face model of the surrounding rock-lining-tunnel system was established based on the No.1 Baoanying Tunnel in Mipan Section of Chengdu-Kunming Railway,and the blowdown and cooling aging of ventilation under different air supply speeds and temperatures was studied by numerical simulation method.The spatio-temporal variation law of CO concentration and temperature distribution in tunnel ventilation was obtained:(1)Under the ventilation temperature of 15℃,the emptying time of CO produced by blasting within 100 m from the tunnel face decreases with the increase of the wind speed.The wind speed of 15 m/s only needs about 350 s,the wind speed of 10 m/s needs about 550 s,and the wind speed of 5 m/s needs ventilation for 30 minutes,which is difficult to meet the requirements of blowdown construction.(2)Under the ventilation temperature of 15℃,the wind speed greater than or equal to 5 m/s can reduce the temperature in the tunnel to the construction demand,and the cooling effect of 10.5 m/s and 15 m/s is similar,while the cooling effect of 5 m/s is poor.(3)Under the design ventilation wind speed of 9.61 m/s,the time for the tunnel temperature drop within 200 m from the tunnel face will increase with the increase of the wind temperature.The time of 15℃and 20℃wind temperature is about 160 s and 170 s,respectively,while the 25℃wind temperature can only make the air temperature within 150 m away from the tunnel face meet the standard requirements.