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. Tianshan Shengli tunnel, with a total length of about 22 kilometers, is currently the longest highway tunnel under construction in China. Started in 2020, the tunnel, a six-year project on the Urumqi-Yuli highway, passes through a cold and high altitude zone, with harsh climate and geological condition. (Xinhua/Hu Huhu)
