The effect of width and slope in uniclinal V-shaped underground space on air transport and smoke characteristics under thermal stack effect

Uniclinal V-shaped structures are common in underground spaces such as mines, tunnels, and subway stations, but few studies have paid attention to its fire smoke movement law. The paper focused on the relationship between air transport velocity, smoke backlayering length, and maximum smoke temperature rise with underground space width and slope. The air transport velocity was quantified, the forecasting model of smoke backlayering length was proposed, and the pattern of variation in the maximum temperature rise was unveiled. The findings indicated that the air transport velocity relates to slope height and buoyancy flux per unit width. The slope has a great influence on the air transport velocity. For the low heat release rate, the backlayering length is primarily determined by the underground space geometry, while for the high heat release rate, it is influenced by the air transport velocity. In contrast to the horizontal underground space, the maximum smoke temperature rise of the uniclinic V-shaped underground space exhibited a linear decrease. When the dimensionless slope height is less than or equal to 1.2, the maximum temperature rise is independent of the section width. When the dimensionless slope height is greater than or equal to 1.6, the maximum temperature rise decreases with the lessening of the section width. These findings contribute to a better understanding of smoke movement in uniclinic V-shaped underground spaces under natural ventilation and provide valuable guidance for smoke control strategies.