Smoke extraction improvement of mid-tunnel shaft by a slim board beneath the shaft and bevel-angle connection

According to the copious research conducted on emergency ventilation in tunnel during fire, when plug-holing and boundary layer separation occur, the actual smoke extraction efficiency is unable to satisfy the emergency ventilation design criteria in tunnels. By and large, so necessary and precious is it that a novel method would be presented in order to improve smoke extraction efficiency of ventilation systems with vertical mid-tunnel shafts...