On April 1, after 980 days of intensive and well-organized construction, the Xinshangjiagou Tunnel of the Xi'an-Yan'an High-Speed Railway, built by China Railway 21st Bureau Group, was successfully holed through, laying a solid foundation for the full completion and opening of the Xi'an-Yan'an High-Speed Railway project in October 2025.

　　The Xinshangjiagou Tunnel is located in Baota District, Yan'an City, with a total length of 1,450 meters and a design speed of 350 km/h. It is a single-tube, double-track tunnel. The area lies in a loess ridge-and-gully region; the tunnel passes through a loess gully in a shallow-buried form, with a maximum burial depth of about 130 meters, and at its shallowest point the crown is exposed at the ground surface.

　　"The Xinshangjiagou Tunnel of the Xi'an-Yan'an High-Speed Railway is adjacent to the existing Shangjiagou Tunnel of the Baotou-Xi'an Railway, with the closest distance less than 30 meters, and it passes beneath Nanniwan Airport. The tunnel excavation involves high risks and extremely stringent quality and safety requirements," said Zhong Zehua, deputy chief engineer of the Xi'an-Yan'an Railway project of China Railway 21st Bureau. To avoid the impact of vibration and noise from blasting on the Baotou-Xi'an Railway and Nanniwan Airport during construction, the project department optimized the excavation method from the traditional drill-and-blast method to excavation using a cantilever roadheader. This is also the first tunnel on the entire Xi'an-Yan'an High-Speed Railway to be excavated with a cantilever roadheader. In addition, the tunnel is equipped with safety facilities and equipment such as a 5G-signal video monitoring system, sound-and-light alarm system and emergency call system, as well as intelligent equipment including intelligent hydraulic trolleys and self-propelled invert trestles, ensuring the safety and quality of tunnel construction.

　　"Since there are very few cases in China of railway tunnels excavated with cantilever roadheaders, we have taken the cantilever roadheader excavation of the Xinshangjiagou Tunnel as a research topic," Zhong Zehua said. Relying on this tunnel, the research project "Research on Key Technologies for Mechanized Construction of Railway Tunnels" adopted methods including literature review, on-site investigation, on-site testing, theoretical analysis and numerical simulation, producing five high-level papers, applying for two patents and applying for one construction method, accumulating valuable experience for subsequent mechanized excavation technology for tunnels in China.