Road construction manager Li Xiaoming arrived in the Xinjiang Uygur autonomous region 18 months ago to help oversee the excavation of a tunnel through the snow-capped Tianshan Mountains. Since then, he has faced flooding, communication blackouts and sleepless nights in bone-chilling temperatures below -20 C.

Yet, Li said the hardships are worthwhile. The 15.7-kilometer West Tianshan Super-Long Tunnel, part of an expressway connecting southern and northern Xinjiang, is progressing as planned.

"We are working toward the goal of breaking through around July of 2026 and completing supporting facilities in the following months," Li said. "The tunnel's success will be critical for the entire expressway to begin operations by late October 2027."

The Tianshan Mountains, one of the world's longest ranges, divide Xinjiang into northern and southern regions. The West Tianshan Super-Long Tunnel extends from Yili Kazak autonomous prefecture to Aksu prefecture and is the most significant section of the G219 highway.

Once completed, the tunnel will cut travel time between Yili and Aksu from 1,710 km to less than 500 km. The shortened distance is expected to boost tourism, improve convenience for local residents and drive economic development, according to China Communications Construction Co, which is overseeing the project.

Sun Zhanjun, deputy project manager, said the unique geological conditions of the region have posed technological, safety and environmental challenges.

"The tunnel runs as deep as 2,365 meters, increasing the risk of rock bursts and spiking temperatures to 43 C at the deepest stretch," Sun said.

Its location in a seismically active region has required additional measures to ensure structural stability and worker safety, he said.

Despite the harsh conditions, crews stationed at one end of the tunnel in Aksu's Wensu county are capable of drilling 18.5 meters per day on average, largely due to a custom-built tunnel boring machine.

The domestically developed machine, which has a cutting diameter of 8.83 meters and a length of 253 meters, weighs 1,800 metric tons. It was transported from a factory in Jiangsu province to Xinjiang in June 2023, with assembly and transportation taking nearly 50 days.

The machine incorporates special designs to enhance torque and thrust, large cooling systems, and monitoring and early warning systems for rock bursts, Sun said.

"Manual blasting and drilling methods typically achieve 6 to 7 meters per day. With this machine, we've progressed 3,400 meters since July," he said.

The tunnel is the nation's first to carve a straight path under vast glacial regions, presenting further environmental challenges.

"Working in a glacial area requires careful environmental planning and readiness for glacial snowmelt," Sun said.

To mitigate these risks, new battery-powered electric vehicles have been deployed at the construction site, and the tunnel's drainage systems have been reinforced to handle heavy water inflows.

Li said he had initial doubts about working in the remote mountains after a grueling five-hour ride from the nearest county, but now he feels optimistic about the project.

"Our accommodations have improved significantly, and more importantly, construction is on track and progressing well," he said.