On May 23, the left tube of the Lianfeng Tunnel—the longest tunnel on the Dayong Expressway constructed by the China Railway Tunnel Group—achieved full breakthrough, laying a solid foundation for the entire line to open to traffic on October 1, 2024.

As a controlling project of the entire line, the Lianfeng Tunnel has a left tube 10,995 meters long and a right tube 11,000 meters long. The tunnel structure lies in an erosional middle-mountain landform with great topographic relief. The tunnel site area features well-developed karst and abundant groundwater, with a maximum water inflow of 46,300 cubic meters per day for a single tube. The tunnel passes through both limbs and the axis of the Shaozhai syncline; the first 2 kilometers from the tunnel portal traverse carbonate rock strata. The maximum longitudinal slope of the inclined shaft is 9.3%. During construction, geological hazards such as karst collapses, large deformations, fault fracture zones, sudden water inrushes, high ground temperatures, and rockbursts occurred frequently, posing extremely high safety risks.

As a key project of Zhaotong City, the Dayong Expressway, once completed and open to traffic, will end the history of Yongshan County having no expressway access and achieve the goal of every county in Zhaotong having expressway access. It will greatly improve travel conditions for residents of six townships in Daguan and Yongshan counties, and is of great significance for accelerating the economic and social development of the two counties and consolidating local poverty alleviation achievements.