Effect of Mechanical Ventilation and Ground Temperature on Anti-Freezing Length of Tunnels in Cold Regions
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摘要:
为揭示通风参数及地温对寒区隧道冻害的影响,基于传热学理论推导了隧道围岩-衬砌-风流三维非稳态数值传热控制方程,分析了不同节点的数值传热差分方程,建立了高地温寒区隧道三维温度场数值计算模型;基于数值分析研究了机械通风速度、机械通风时间和地温对高地温寒区隧道防冻长度的影响. 结果表明:1) 不考虑机械通风,孜拉山隧道的防冻长度超过1200 m;地温每升高5 ℃隧道防冻长度将减小约100 m. 2) 考虑机械通风影响,当地温为10~30 ℃时,每天以2.5 m/s的速度通风2.0 h可减少防冻长度215 m;不同地温下机械通风速度每增大0.5 m/s,防冻长度减小约20 m,地温对防冻长度衰减速率影响很小;当机械通风时间小于2.0 h时,不同地温条件下增大机械通风速度对防冻长度的影响不大.
Abstract:In order to reveal the effect of ventilation parameters and ground temperature on freezing damage in tunnels in cold regions, the three-dimensional unsteady numerical heat transfer control equations for the tunnel surrounding rock, lining, and airflow are developed based on heat transfer theory. The numerical heat transfer difference equations of different nodes are analyzed, and a three-dimensional temperature field numerical calculation model is established for tunnels in cold regions with high ground temperatures. The effect of mechanical ventilation velocity, mechanical ventilation time, and ground temperature on the anti-freezing length of tunnels in cold regions with high ground temperatures is studied based on numerical analysis. The results show that 1) without considering mechanical ventilation, the anti-freezing length of Zilashan tunnel will exceed 1 200 m and decrease by about 100 m when the ground temperature increases by every 5 ℃. 2) By considering the effect of mechanical ventilation, when the ground temperature is 10–30 ℃, ventilation at a speed of 2.5 m/s for 2.0 h per day can reduce the anti-freezing length by 215 m; the anti-freezing length decreases by about 20 m as mechanical ventilation velocity increases every 0.5 m/s under different ground temperatures, and the effect of ground temperature on the decay rate of anti-freezing length is slight; when the mechanical ventilation time is less than 2.0 h, increasing mechanical ventilation velocity under different ground temperature conditions has little effect on anti-freezing length.
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表 1 昌都地区气温参数(近20年)
Table 1. Temperature parameters in Changdu area (nearly 20 years)
℃ 月份 1月 2月 3月 4月 5月 6月 7月 8月 9月 10月 11月 12月 均温 −1.6 1.0 4.7 8.1 12.2 15.3 16.3 15.5 13.1 8.4 2.4 −1.5 最低均温 −9.6 −6.8 −2.4 1.4 5.3 9.2 12.6 10.0 7.3 1.8 −5.0 −9.3 表 2 数值计算工况
Table 2. Numerical calculation conditions
工况 机械通风风
速/(m·s−1)每天机械通
风时间/h地温/℃ 1~5 0 1.0,1.5,2.0,
2.5,3.0孜拉山实
际地温6~10 2.5 11~15 3.0 16~20 3.5 21~25 4.0 26~30 0 2.0 10,15,20,
25,3031~35 2.5 36~40 3.0 41~45 3.5 46~50 4.0 -
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