Blocking the tunnel portal is one strategy in railway tunnel firefighting. In order to evaluate the effect of tunnel portal sealing ratio on fire behaviour, Fire Dynamics Simulator (FDS) was used to simulate tilted tunnel fire with different slope angles varying from 0% to 5%, heat release rate varying from 10 to 50 MW and sealing ratios varying from 0% to 75%. Results show that the experimental data of the temperature distribution inside the tilted tunnel were in good agreement with the simulation results. Moreover, the ceiling temperature rise decreases along the tunnel with the increase of the tunnel portal sealing ratio at initial stage and then tends to stabilize because of less oxygen supply when the heat release rate is relatively large. The maximum temperature rise decays exponentially along the tunnel ceiling with distance. The current model for temperature decay beneath the tunnel ceiling was proposed to be modified by taking the tunnel entrance sealing ratio into account. The predictions by the modified model agree well with the experimental measurement. The results could provide practical information and knowledge in ventilation system design and emergency evacuation for inclined railway tunnels.

封堵隧道口是铁路隧道消防的一种策略。为了评估隧道洞口密封比对火灾行为的影响，火灾动力学模拟器（FDS）被用来模拟倾斜的隧道火灾，不同坡度从 0% 到 5% 变化，放热率从 10 到 50 MW 和密封比从 0% 到 75% 不等。结果表明，倾斜隧道内温度分布的实验数据与模拟结果吻合较好。此外，随着隧道洞口封闭比的增加，隧道顶温升沿初期逐渐降低，然后随着放热率较大时供氧量减少而趋于稳定。最大温升沿隧道天花板随距离呈指数衰减。建议通过考虑隧道入口密封比来修改隧道天花板下温度衰减的当前模型。修改后的模型的预测与实验测量结果非常吻合。研究结果可为倾斜铁路隧道通风系统设计和应急疏散提供实用信息和知识。