It was recently learned that the Nanjing Xuanwu Lake Tunnel, which underwent its first major overhaul in 20 years, has had 85% of its wall decorative panels replaced and 85% of its foam-water spray fire extinguishing system piping installed after more than half a year of renovation, with over 75% of the total workload completed.

At 1 a.m. inside the Xuanwu Lake Tunnel, workers were carrying out their respective duties. Some were replacing the decorative panels on both sides of the tunnel, while others were installing new ground expansion joints. Since the renovation began on November 1, 2023, the entire maintenance work plan has been scheduled to last one year. Work is carried out daily from 0:00 to 5:30, and motor vehicles pass through normally during the remaining hours.

It is understood that this internal facility upgrade and renovation will involve centralized treatment of defects existing in the tunnel, introduce a foam-water spray fire extinguishing system for tunnel fire protection, and update the automatic fire alarm system and emergency lighting system, among others, effectively enhancing the tunnel's fire prevention and control capabilities.

At present, the foam-water spray fire extinguishing system, composed of components such as fire water pipes, foam pipes, spray nozzles, dual-band infrared flame detectors, and intelligent control boxes, has basically been completed. The Xuanwu Lake Tunnel was completed and put into use in 2003, and its internal facilities have shown signs of aging. In particular, the tunnel currently has only one fire protection system, which is manually operated and cannot handle emergencies in the shortest possible time. The newly added extinguishing system has a spray device installed every 5 meters, each containing 3 nozzles, covering 3 lanes, with a maximum range of 12 meters. According to the person in charge of the construction unit, when an emergency such as a vehicle spontaneous combustion occurs inside the tunnel, the early warning system is triggered, and fire water and foam then enter the control box to mix, delivering the foam-water to the spray system at the top of the tunnel. From fire detection to spray suppression, the response is expected to be completed within 45 seconds. The two fire protection systems work in tandem, installing a "double insurance" for the tunnel's fire safety.

On the renovated tunnel walls, many eye-catching LED display screens have been added. According to reports, once put into use, these screens will display the distance to the nearest escape passage entrance, pointing out a "green escape route" for trapped persons.

The escape doors in the tunnel have also been upgraded from the original silver to a striking orange, with green escape signs added on both sides of the doors, making them more conspicuous and vivid. There are a total of 90 escape passage entrances in the tunnel, one approximately every 50 meters, making it convenient to choose the nearest emergency refuge. The comb-tooth expansion joints that had been "on duty" in the tunnel for 20 years have also been replaced with Maurer expansion joints this time. Compared with traditional expansion joints, the new type is easier to replace and maintain later, effectively reducing the noise of passing vehicles and meeting the demand for rapid vehicle passage.

In addition, the tunnel wall decorative panels have been replaced with fire-resistant enamel steel plates rated Class A for flame retardancy, and the emergency lighting system has been updated to high-efficiency, energy-saving LED lights. This series of renovations not only gives the tunnel a better appearance but also makes it smarter and safer.

In 2023, Nanjing took the lead nationwide in issuing the "Nanjing Urban Traffic Tunnel Fire Protection Design Guide (Trial)". The Xuanwu Lake Tunnel became the first project to carry out fire safety enhancement design in accordance with the Guide and relevant current national technical standards, and it also provides "practical" experience for the fire protection system upgrade and renovation of existing tunnels in the city, continuously improving emergency response capabilities for tunnel fire prevention and control.