Abstract The plug-holing phenomenon in naturally ventilated tunnel fires with vertical shaft has been receiving considerable attention, however, there is still no simple physical quantity to represent the degree of plug-holing. A series of numerical simulations were conducted to analyze the ventilation performance of vertical shaft in tunnel fires by considering different shaft geometries. Plug-holing height and complete plug-holing were proposed to describe the degree of plug-holing. The influences of shaft geometry on smoke extraction efficiency and plug-holing height were likewise analyzed. Results show that the total mass flow rate in the vertical shaft increases with the increase of shaft length and height, and is more sensitive to shaft length. By contrast, the increase in the pure smoke in the shaft is relatively limited. Moreover, the dimensionless plug-holing height is considerably sensitive to and significantly increases with the shaft length. However, the dimensionless plug-holing height has lower sensitivity to the shaft height and shows no evident monotony with a change in shaft height. Accordingly, a prediction model of the dimensionless plug-holing height is eventually established on the bases of simulated data. Critical criteria for determining the occurrence of complete plug-holing in car fire scenarios have been identified and can be described as Ri ∗ 0.09 α 1.22 = 5.16 .

中文翻译：

---

竖井自然通风隧道火灾的塞孔高度及完全塞孔现象

摘要 竖井自然通风隧道火灾中的堵孔现象一直受到广泛关注，但目前还没有简单的物理量来表示堵孔程度。通过考虑不同竖井几何形状，进行了一系列数值模拟，以分析隧道火灾中竖井的通风性能。提出了塞孔高度和完全塞孔来描述塞孔程度。同样分析了竖井几何形状对排烟效率和塞孔高度的影响。结果表明，竖井总质量流量随着竖井长度和高度的增加而增加，对竖井长度更为敏感。相比之下，竖井中纯烟的增加相对有限。而且，无量纲的塞孔高度对轴长度非常敏感，并且随着轴长度的增加而显着增加。然而，无量纲的塞孔高度对轴高的敏感性较低，并且随着轴高的变化没有明显的单调性。据此，最终在模拟数据的基础上建立了无量纲塞孔高度的预测模型。确定汽车火灾场景中发生完全堵塞的关键标准已经确定，可以描述为 Ri ∗ 0.09 α 1.22 = 5.16 。最终在模拟数据的基础上建立了无量纲塞孔高度的预测模型。确定汽车火灾场景中发生完全堵塞的关键标准已经确定，可以描述为 Ri ∗ 0.09 α 1.22 = 5.16 。最终在模拟数据的基础上建立了无量纲塞孔高度的预测模型。确定汽车火灾场景中发生完全堵塞的关键标准已经确定，可以描述为 Ri ∗ 0.09 α 1.22 = 5.16 。