白鹤滩水电站尾水隧洞施工通风效果研究

Study on construction ventilation effect of Baihetan hydropower station tail water tunnel

白鹤滩水电站右岸尾水隧洞平均埋深400m以上,第Ⅰ层开挖采用独头掘进方式,无进、排风竖井和平洞,通风线路结合施工支洞布置,不具备设置射流风机接力通风条件,一站式最远通风距离达3700m,施工通风十分困难。为确保通风效果,计算了各施工工序需风量,采用Fluent流体数值软件,建立了三维、非稳态的大埋深独头隧洞气体湍流模型,对爆破通风流场形态和污染物逸散、分布规律进行了研究,并通过现场污染物测试进行了验证。研究表明:尾水隧洞通风2min后流场基本稳定,掌子面爆破后污染物浓度先急剧增加,之后随着时间的增加不断降低。通风12min后,掌子面3m附近污染物浓度满足规范要求;15min后,所有部位污染物浓度均接近规范允许范围,气流组织顺畅,通风效果良好。

The average depth of Baihetan Hydropower Station right bank tail water tunnel is more than 400 m;therefore, layer Ⅰexcavation adopts blind heading method, no wind shaft and tunnel, and ventilation lines are combined with construction branches,and can't set jet fans. The maximum one-stop adjective ventilation length is 3700 m, so the construction ventilation is very difficult. In order to ensure the ventilation effect, we calculated the air volume of each construction process. Using Fluent fluid numerical software, we established deep burying blind heading three dimensional and unsteady turbulent caverns model to study the blasting flow pattern and pollutants dispersion, distribution law, and verified using in-situ pollutant concentration field test. The results showed that tail water tunnel flow field is basically stable after 2 min ventilation. After excavation face blasting, pollutant concentration increases sharply, then decreases. After ventilation 12 min, pollutant concentration near tunnel face 3 m met standard requirement. After 15 min, pollutant concentration in all part was close to the standard allow scope. Air flow was smooth and ventilation effect was good.