On March 2, 2021, after more than 1400 days and nights of intensive construction, the tunnel from Sunan, Zhangye, G213 line to Dongshan, Qilian, Qinghai Province was smoothly connected with a loud sound. Builders at both ends of the tunnel waved red flags, shook hands and hugged each other to celebrate the smooth completion of the tunnel.

The Dongshan tunnel, which runs through Gansu and Qinghai provinces, with a total length of 3639 meters, started from Baizhuangzi Village, Sunan Yugur Autonomous County, Gansu Province ended in the Yeniugou Village, Qilian County, Qinghai Province. It is a key project of Suqi Highway of G213 line. The tunnel project is located at an average elevation of 4000 meters, the air oxygen content is low to 11%, and the lowest temperature in winter is below 30 ℃. The project is constructed from both sides of the watershed in Gansu and Qinghai. Faced with extremely complex geological conditions, great construction difficulties, high technical requirements, tight construction period and other difficulties, the constructors of China Railway No.4 Engineering Group Co., Ltd. overcame the plateau reaction, did not fear the cold, worked overtime, worked in turns, excavated the tunnel, constructed the track and other projects in an orderly manner, so as to ensure that the whole line can be opened to traffic in June this year.

It is reported that G213 line is one of the 47 north-south vertical lines of ordinary national roads in the national highway network planning which starts from Ceike, Inner Mongolia in the north, ends in Mohan, Yunnan in the south, and connects with Qilian, Qinghai Province after passing through Jiuquan and Sunan in Gansu Province. The section from Zhangye Sunan to Qilian, Qinghai Province is an important part of it. After the completion of the highway, it will open up the corridor from western Gansu to Qinghai, break the traffic bottleneck, link Qinghai and western Gansu into one, speed up the development of the corridor economy and tourism industry, and enhance the transportation capacity of the production and living materials of the farmers and herdsmen along the line and the fire prevention and disaster relief capacity of the natural forest region of Qilian Mountain Nature Reserve.