Photo shows a view of vehicles at the exit of the Tianshan Shengli Tunnel along the Urumqi-Yuli Expressway in northwest China’s Xinjiang. (Photo by Zhao Huafeng)

On the seventh day of the Chinese New Year, travelers embarked on their return journeys. Inside the Tianshan Shengli Tunnel, the crucial section of the G0711 Urumqi-Yuli Expressway, lights shone brightly as vehicles filled with the weight of loved ones' hopes shuttled back and forth.

Facing its first Spring Festival travel rush, this world's longest expressway tunnel has become a major transportation artery connecting northern and southern Xinjiang. During the holiday period, the average daily traffic volume exceeded 34,000 vehicles, peaking at over 45,000 vehicles per day.

Amidst the snowy Tianshan Mountains with temperatures dropping to minus 30 degrees Celsius, how did the Tianshan Shengli Tunnel successfully pass its first major test and achieve smooth operation in such an extreme cold environment?

"We have tailored a comprehensive 'super anti-freezing' system for the tunnel to safeguard travel during the cold snap of the Spring Festival rush," introduced Miao Baodong, Chief Engineer of China Communications Construction Company (CCCC) Xinjiang Transportation Investment Development Co., Ltd.

First, the pipes are given a "thermal coat" to ensure the drainage system operates normally.

"The biggest concern for long tunnel traffic is pipe freezing," said Miao. Especially in winter, moisture accumulated in the mountain during summer can seep through the tunnel roof and lining, freezing into ice and posing a safety hazard to traffic.

The construction team excavated ultra-long and deep-buried central drainage ditches at the tunnel entrances and exits. The deep-buried design keeps the ditches away from the frost zone, reducing the risk of icing at the source. Simultaneously, all lateral drainage pipes connected to the ditches are wrapped in flexible foam rubber-plastic insulation material, like giving the pipes a "thermal coat," preventing water inside from freezing and blocking, thus ensuring the drainage system operates around the clock in all weather.

Next, a thick "cold-proof wall" is built at the tunnel entrances to prevent the tunnel structure from freezing and cracking.

The tunnel entrance is the thermal interface making it a critical point for frost protection. With high altitudes, The Tianshan Mountains keep low temperatures for about half the year. Traditional localized frost protection measures are insufficient against prolonged extreme cold.

"During the construction phase, we innovatively installed over 500 meters of insulated concrete structure, which acts like a thick 'cold-proof wall,' forming a continuous 'buffer zone' against freezing," Miao said. This not only ensures the stability of the tunnel structure but also creates a safe road surface environment for passing vehicles, serving as a valuable exploration into structural frost protection for long tunnels in high-altitude cold regions.

To be impervious to wind, snow, and freezing, it requires not only a solid foundation, but also diligent upkeep.

Inside the tunnel, vehicles flow in an endless stream, and the large screen presents a comprehensive, real-time holographic view of the tunnel, visible at a glance.

This is the holographic intelligent monitoring center of the Tianshan Shengli Tunnel. Holographic near-and-far cameras deployed inside the tunnel act like sharp eyes. The multiple video streams they capture are fed into the system's "brain" for fusion computing and 3D reconstruction, generating a real-time, dynamic digital twin tunnel on the large screen that can be observed from any angle.

"The Tianshan Shengli Tunnel is long, so a manual inspection takes several hours. The traditional model of 'manual inspection + fixed cameras' is ineffective here," said Qi Zhijun, Project Chief Engineer of CCCC Mechanical and Electrical Engineering Bureau. To manage this super-long tunnel, it was necessary to install a "smart brain" capable of thorough perception, holistic thinking, and rapid response.

Relying on this monitoring network, the tunnel operation team has achieved joint operations and information sharing with meteorological, emergency response, firefighting, and other departments. During the Spring Festival travel rush, personnel are on standby 24/7. In case of an incident, they can respond quickly and provide service guidance, effectively ensuring the smooth passage of the high traffic volume during the rush.

"With this combination of solid infrastructure and software capabilities, even in extreme low-temperature weather, we can ensure critical facilities don't 'strike', building a strong line of defense for safe tunnel operation," Miao said. Now that the tunnel is open, crossing the Tianshan Mountains takes only 20 minutes. With this set of anti-freezing measures, they are committed to safeguarding every hour of tunnel operation, 24/7.

(Source: People’s Daily, Reporter: Han Xin)