Abstract: In order to study the influence of shaft spacing on the ultimate height of the shaft chimney effect during fire, tunnel fires under four shaft cross-section sizes and five shaft spacing were simulated by FDS fire dynamics simulation software, focusing on the influence of shaft spacing on the ultimate height of chimney effect. The results show that the shaft chimney effect is enhanced with the increase of shaft height, but its ultimate height gradually decreases with the increase of shaft spacing; moreover, the influence of shaft spacing on the ultimate height of the shaft chimney effect gradually increases with the increase of shaft cross-section size. Based on the simulation data, the correlation between the limiting height z of the shaft chimney effect and the shaft spacing x and the side length of the shaft section y was obtained. The expression can estimate the ultimate height of the shaft chimney effect when 60 m≤x≤240 m and 0.5 m≤y≤2.5 m under the same environment, which provides guidance for the design of natural ventilation shafts, and is expected to provide a reference for the design of smoke vents of natural ventilation systems in related fields.

Key words: safety engineering, shaft spacing, chimney effect, limiting height, numerical modelling