On June 12, builders work on the construction site of the Qinghuayuan tunnel on the Beijing-Zhangjiakou high-speed railway line in Zhangjiakou, North China’s Hebei province. The last rail was put on the sleeper on the morning of June 12 after seven months of work, representing the completion of the track-laying construction of the Beijing-Zhangjiakou high-speed railway. It is hailed as a demonstration of a smart high-speed railway project, with the most advanced Chinese railway technology being applied.[Photo/Xinhua]

A track is laid in the Qinghuayuan tunnel on the Beijing-Zhangjiakou high-speed railway line in Zhangjiakou, North China’s Hebei province, on June 12. [Photo/Xinhua]

A track is laid in the Qinghuayuan tunnel on the Beijing-Zhangjiakou high-speed railway line in Zhangjiakou, North China’s Hebei province, on June 12. [Photo/Xinhua]

A photo taken on June 12 shows the tracks are completed in the Qinghuayuan tunnel on the Beijing-Zhangjiakou high-speed railway line in Zhangjiakou, North China’s Hebei province, on June 12. [Photo/Xinhua]

A photo taken on June 12 shows the tracks are completed in the Qinghuayuan tunnel on the Beijing-Zhangjiakou high-speed railway line in Zhangjiakou, North China’s Hebei province, on June 12. [Photo/Xinhua]