采用因次分析方法推导了地铁区间隧道火灾烟气逆流长度的无因次表达式;以重庆地铁 6 号线为例，开展了区间隧道形状的调查，选择了 9 种不同断面形式的区间隧道，采用 FDS5．5 模拟计算了隧道火灾烟气运动状况，进而提出了烟气逆流长度和临界风速的预测模型，并进一步建立了几何比例尺为1∶ 10 的地铁区间隧道模型实验台来开展小尺寸试验研究．结果表明:文中提出的烟气逆流长度和临界风速的预测模型的模拟结果与小尺寸试验结果吻合较好;相比于文中提出的临界风速预测模型的预测结果，现有的预测模型预测的临界风速偏小．

In this paper,first,the dimensionless expressions of the smoke backlayering length and the criticalvelocity in metro tunnels were deduced via a dimensional analysis.Then,nine tunnels with different cross sectionswere employed according to the survey results from the tunnel form of the Metro Line 6 in Chongqing,China,andthe smoke flow in the tunnels was analyzed with FDS5.5.Finally,the prediction models of the smoke backlayeringlength and the critical velocity were established,and a 1/10 scale model tunnel was built to carry on small- scalemodel experiments.The results show that the results obtained by the proposed prediction models accord well withthose of small- scale model experiments,and that the critical velocity predicted by the existing method is underesti-mated.