The team adopted the construction pattern of three drifts and four shafts, according to China Communications Construction Xinjiang Transportation Investment and Development Co, which built the tunnel.

As the final 3 meters of rock gave way, the two teams of workers — one from the north, the other from the south — met in the middle, their cheers echoing through the tunnel. "We've finally conquered this 'hard bone,'" says Mao Jinbo, chief engineer at the tunnel's exit, his voice trembling with emotion.

But the challenges extended beyond engineering. The harsh environment tested the resolve of the workers. To boost morale, the project team transformed an old railway station into vibrant living quarters. With dormitories, restaurants and supermarkets, it became a home away from home for workers. "We came from all corners of the country but here, we became family," says Cheng Liumin, who managed the area.