Workers transport steel arches at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021. (Xinhua/Hu Huhu)

A worker takes off his raincoat to disperse the moisture from his sweater and trousers at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

Workers install steel arch frame at the bottom of hard rock roadheader at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

A worker is seen at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

A worker lays inverted arches at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

The seepage of the mountain inside the tunnel drops on a worker's helmet at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

A worker uses the remote control to operate the drilling rig to drill holes in the tunnel at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

A worker talks with his colleague by walkie-talkie at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.

A worker takes a short break at the construction site of Tianshan Shengli tunnel in northwest China's Xinjiang Uygur Autonomous Region, Feb. 4, 2021.