青岛第二海底隧道通过在隧道的南北线排烟道上纵向间隔设置联络烟道，将南北线烟道联通。由于目前尚无公路隧道设置联络烟道的案例可供参照，为研究联络烟道对公路隧道防排烟效果的影响，亟需明确在不同联络烟道间距下隧道内火灾温度场、烟气蔓延情况、系统阻力等的分布规律，确定最优联络烟道间距。在现有评价指标烟气蔓延长度l₆₀、排烟效率η的基础上提出阻力削减率ξ，构建基于性能化的联络烟道间距优化评估模型；在调研全国各种隧道横通道间距设置配合形式后，采用Fluent软件模拟不同联络烟道间距下的烟流特性及数据。结果表明： 1）联络烟道能有效降低排烟系统的阻力； 2）随着联络烟道间距的缩短，烟气蔓延长度l₆₀由260 m缩小至180 m，排烟效率η由93.39%提升至97.80%，阻力削减率ξ由15.42%减小至2.20%； 3）联络烟道间距为750 m和1 500 m混合的设置方式能起到较好的排烟效果，此时继续缩短联络烟道间距对系统排烟能力提升有限。

Longitudinal connecting flues connect the flues of the north and south line tunnels of the Qingdao 2nd subsea tunnel. This work is the first attempt in a highway tunnel. To examine the effect of connecting flues on the smoke exhaust of highway tunnels, various spacings between connecting flues are set to explore the distribution patterns of fire temperature field, smoke spread, and system resistance and determine the optimal spacing of connecting flues. Based on the evaluation indices, including smoke spread length and smoke exhaust efficiency, the resistance reduction rate is proposed for the construction of an effective evaluation model for the spacing between connecting flues. Furthermore, the configuration forms of various spacing settings between cross passages in China are investigated and the Fluent software is employed to simulate smoke flow characteristics at various connecting flue spacings. The results reveal the following: (1) The connecting flues effectively reduce the resistance of the smoke exhaust system. (2) With shortening of the connecting flue spacing, the smoke spreading length decreases from 260 to 180 m, the smoke exhaust efficiency increases from 93.39% to 97.80%, and the resistance reduction rate decreases from 15.42% to 2.20%. (3) The combined use of 750 and 1 500 m connecting flue spacings exhibit a better smoke exhaust effect than small spacing.