Analysis of the Stability of the Double-Hole Complementary Ventilation and Ventilation Network of the Tunnel Constructed by Drilling and Blasting Method

Abstract

Currently, double-hole complementary ventilation is a mature ventilation method for operating tunnels, but how to carry out it in the construction tunnel poses a new challenge. Due to the desynchronization in the construction period of the double-hole tunnel, there is an instantaneous difference in the air flow demand between the two working faces. The study analyzes the impact of geometric parameters, specifically Lt (the distance from the traffic cross passage to the working face of the advance side tunnel), Lp (the distance between the pedestrian cross passage and the working face of the advance side tunnel), Ht (height of the upper step), and Lw (safe step distance of the double-hole working face) on ventilation network stability. The results show that with the increase of Lt and Lp, the Rm resistance of each branch changes non-uniformly, and the stability of the ventilation network is significantly different. Then, when Lt, Lp = 80 and 180 m, the air flow directions of the double-hole tunnel are the same. Finally, when Lt and Lp = 130 m, the air flow directions are inconsistent, which indicates that in the range of 80 m < Lt or Lp < 180 m, the cross-section size of the cross passage affects the stability of the ventilation network. However, when 2.5 m < Ht < 3 m, or 30 m < Lw < 50 m, the stability of the ventilation network is not affected, and the flow field of the double-holes does not interfere with each other. The conclusions obtained confirm that the double-hole complementary ventilation method is available in construction tunnels, and has potential for implementation.