Changing burning area of spill fire may cause chain effects and expand consequences in tunnels, which poses a greater challenge to personnel escape and rescue. Research on tunnel spill fire is needed to reveal its behavior and internal mechanisms. This paper carried out a series of continuous spill fires on fireproof glass both in tunnel environment (TE) and open environment (OE). The spread, burning, and heat transfer characteristics were compared between these two environments. The results showed that spread areas of TE spill fires in quasi-steady stage were smaller than those of OE. The burning rate enhancement coefficients ranged from 0.92 to 1.76 from small spill fires and larger ones in tunnel. With respect to penetrating heat radiation and heat conduction loss, TE spill fires were slightly larger than OE spill fires. And it was proved that the heat feedback is the main cause for the burning rate enhancement in tunnel. Then a semi-empirical model was proposed by coupling the spread, burning and heat transfer process. The model was proved to be quite accurate by validating with experimental data.

改变溢出火的燃烧面积可能会导致连锁效应，并扩大隧道的后果，这对人员逃生和救援构成了更大的挑战。需要进行隧道溢火研究以揭示其行为和内部机理。本文在隧道环境（TE）和开放环境（OE）中对防火玻璃进行了一系列连续的起火。比较了这两种环境的扩散，燃烧和传热特性。结果表明，准稳态阶段TE溢火的蔓延面积小于OE。较小的溢火和较大的隧道火灾，燃速提高系数在0.92至1.76范围内。关于穿透热辐射和热传导损失，TE溢火比OE溢火略大。事实证明，热反馈是提高隧道燃速的主要原因。然后结合扩散，燃烧和传热过程提出了一个半经验模型。通过实验数据验证，该模型非常准确。