On May 13, the left tube of the Altun Mountain Tunnel in Section II of the Dundang Pilot Project reached 7,416 meters of excavation, entering the final 100-meter sprint before breakthrough.

The Altun Mountain Tunnel in Section II of the Dundang Pilot Project, constructed by Gansu Road & Bridge Construction Group with a total investment of 1.299 billion yuan, is a controlling project of the Dundang Expressway. It is an extra-long rock tunnel in a high-cold, high-altitude area of Gansu Province, with a total length of 15,052 meters, of which the left tube is 7,527 meters and the right tube is 7,525 meters.

Since the start of construction, the contractor of Section II of the Dundang Pilot Project, Gansu Road & Bridge Construction Group, has overcome numerous difficulties such as fractured surrounding rock, large deformation of soft rock, small-block structural collapse, high ground stress and water inflow. Based on actual site conditions, project managers have commanded from the front, made careful arrangements and thorough deployments, and steadily advanced construction progress while ensuring project quality and construction safety.

The Altun Mountain Tunnel is a key controlling project of the Dunhuang–Dangjinshan Expressway, a connecting line between the national Beijing–Tibet Expressway and the Lianyungang–Khorgas Expressway (G30), and an important corridor linking Gansu and Qinghai provinces. Once the Altun Mountain Tunnel is holed through, the entire line will be fully connected.