Temperature rise induced by tunnel fire is a key factor injuring persons and destroying the tunnel lining structure as well as the facilities. In order to better comprehend the temperature distribution induced by fire in branched tunnel, a series of reduced scale experiments with different longitudinal ventilation velocity and bifurcation angles were conducted to investigate the temperature longitudinal decay in mainline tunnel and ramp in this paper. The heat release rate varied from 1.72 kW to 6.04 kW corresponding to 3.07 MW–10.8 MW in full scale. Three bifurcation angles of 5°, 10°, and 15° were considered to investigate the effect of bifurcation angle on temperature longitudinal distribution in branched tunnel. Results show that the bifurcation angle influences temperature distribution between fire source two sides due to the asymmetric air entrainment. The increasing of heat release rate results in the higher temperature under natural ventilation. The ventilation velocity had a greater enhancing effect on the temperature rise in mainline tunnel due to smoke accumulation effect at downstream of fire source. The exponential correlation is proposed to predict the longitudinal temperature beneath the tunnel ceiling not only in mainline tunnel but also in ramp by taking the bifurcation angle into consideration.

隧道火灾引起的温度升高是造成人员伤亡和隧道衬砌结构及设施破坏的关键因素。为了更好地了解支线隧道内火灾引起的温度分布，本文通过一系列不同纵向通风速度和分岔角度的缩尺实验，研究了干线隧道和匝道内温度的纵向衰减。热释放率从 1.72 kW 到 6.04 kW 不等，对应于 3.07 MW–10.8 MW 满量程。考虑了5°、10°和15°三个分叉角，研究了分叉角对支管内温度纵向分布的影响。结果表明，由于不对称的空气夹带，分叉角会影响火源两侧的温度分布。放热率的增加导致自然通风下温度升高。由于火源下游烟气聚集效应，通风速度对干线隧道温升有较大的促进作用。考虑到分岔角，提出指数相关预测隧道顶板下方的纵向温度，不仅在干线隧道中，而且在匝道中。由于火源下游烟气聚集效应，通风速度对干线隧道温升有较大的促进作用。考虑到分岔角，提出指数相关预测隧道顶板下方的纵向温度，不仅在干线隧道中，而且在匝道中。由于火源下游烟气聚集效应，通风速度对干线隧道温升有较大的促进作用。考虑到分岔角，提出指数相关预测隧道顶板下方的纵向温度，不仅在干线隧道中，而且在匝道中。