On August 26, the Tongbaiyuan No. 3 Tunnel of the Shaanxi Yan-Yu High-Speed Railway officially entered the main tunnel construction stage.

The 6th bid section of the Yan-Yu High-Speed Railway has a total length of 21.96 kilometers, with bridges and tunnels accounting for 90.5%. The Tongbaiyuan No. 3 Tunnel under construction has a total length of 3,013 meters and is located in Kuanzhou Town, Qingjian County, Yulin City. It is a single-tube double-track tunnel and one of the key projects of the entire line.

The Tongbaiyuan No. 3 Tunnel passes through a loess ridge and gully area with highly undulating terrain, where adverse geological conditions such as sinkholes, landslides, and surface slumping exist. The tunnel has a maximum burial depth of 142 meters, and the crown bears considerable surrounding rock pressure. The tunnel body passes through multiple shallow-buried sections, with the shallowest surface cover being 2 to 3 meters. Severe asymmetric loading exists at the entrance portal, and the mountain mass stability is poor. The tunnel inlet and outlet are located within a "U"-shaped valley, and the construction site is narrow. The outlet is adjacent to a national highway with heavy traffic, making construction traffic organization difficult.

According to reports, to ensure smooth construction, the project team has repeatedly invited experts to conduct in-depth on-site surveys and has formulated multiple safe construction plans, including staged excavation, advance pipe-roof support to prevent collapse, strengthened temporary retaining and protection, and backfill grouting, so as to ensure the tunnel enters the portal safely.

The Yan-Yu High-Speed Railway is an important component of the Bao(tou)-(Yinchuan)-Hai(kou) Corridor in the national "Eight Vertical and Eight Horizontal" high-speed rail network and of Shaanxi's "rice-shaped" high-speed rail network. Once completed, Shaanxi will achieve the goal of high-speed rail access in every city. The Yan-Yu High-Speed Railway is of great significance for further promoting a new pattern of western development, improving transportation infrastructure along the line, and advancing high-quality regional economic and social development. It will also provide a convenient passenger transport corridor for western Inner Mongolia and northern Shaanxi to reach the Guanzhong, southwestern, and other regions.