Abstract: Long-term ventilation performance during tunnel construction by drilling and blasting method is challenging. To address this issue, based on optimization of installation and maintenance technologies of ventilation in tunnels, research and application status of installation and maintenance technologies of ventilation fans and ducts are reviewed. The research results indicate the following: (1) When a fan is fixed on a movable mounting base and accurately positioned via horizontal and vertical alignment adjustments, it can facilitate the straight and smooth suspension of the duct from the fan to the tunnel portal, thereby reducing air resistance at the source of installation. (2) Flexible ducts are connected to the fan via elastic straps and clamps, while rigid ducts are connected to fan through flanges. This connection method can prevent duct damage and air leakage at the joints caused by high pressure at the fan outlet. (3) According to the designed position and diameter of the ducts, the installation position and spacing of hook-equipped expansion bolts are determined, a steel wire rope is laid on the hooks, and the duct hanging rings are connected to the steel wire rope with spring buckles to achieve a straight and unobstructed suspension state of the duct in the tunnel. (4) Based on the on-site layout of the intersection tunnel, the installation height and turning angle of the tee structure or wind silo can be determined, and oblique and vertical steel supports or steel wire ropes can be used for suspension and fixation. The tee structure can be connected to air valves and rigid ducts via flanges, and to flexible ducts via hoops, the joints are sealed with gaskets or sealants to ensure duct tightness. (5) It is recommended to reserve the location, shape, and size of the duct holes on the construction trolley, and install protective pipes at the reserved holes. Multiple sets of pulleys are arranged on its sidewalls to replace sliding friction with rolling friction. Meanwhile, curved sections and guide sections equipped with pulleys are installed at the front and rear of the trolley. This setup can prevent the duct from being scratched, damaged, bent, or wrinkled when passing through the protective pipes, and reduce local ventilation resistance. The research conclusions indicate that the quality of installation, operation, and maintenance of fan and duct is the key to maintaining the designed ventilation performance over the long term, and the core of stably ensuring the ventilation effect during tunnel construction.

Key words: tunnel engineering, ventilation, fan, air duct, installation and maintenance technology