Numerical investigation on the smoke extraction performance through natural ventilation via board-coupled shaft in tunnel with multiple burial depth.

Previous studies have discovered that board-coupled shaft (BCS) can eliminate the plug-holing phenomenon that usually occurs in the traditional shaft and could be applied in shallow-buried and deep-buried tunnels. However, the impact of tunnel burial depth on the smoke exhaust performance with BCS is unknown at present. To better understand this question, 42 simulations were conducted, and the effects of buried depths and board locations on the smoke extraction performance of BCS were investigated. The results indicated that: (a) when the buried depth of the tunnel is large enough (≥10 m) that a plug-holing phenomenon occurs, the overall performance of BCS is better than that of the traditional shaft; (b) the smoke extraction performance of the BCS is controlled by both the buried depth of tunnels and the board locations when the shaft height is lower than 10 m, but mainly dominated by the board position when the shaft height is larger than 30 m; (c) the BCS can achieve a maximum 65.5% improvement in smoke extraction performance over the traditional shaft when the shaft height is 10 m. Besides that, a semi-empirical equation was developed to predict the correlation between non-dimensional volume flow rate and buried depth. These studies can guide extending the application scenarios of shafts and providing technical support. • Smoke extraction performance of shafts under different buried depths was studied. • Performance of BCS is mainly dominated by board position in deeper tunnel (≥30 m). • The advantage of smoke extraction performance of BCS decreases as h s increases. • A relationship between dimensionless volume flow rate and buried depth is derived. [ABSTRACT FROM AUTHOR]