On June 16, the Daxu Tunnel on Section 4 of the Chaoma Intercity Railway, constructed by China Railway No. 4 Engineering Group, was successfully holed through, laying a solid foundation for subsequent construction.

It is reported that the Daxu Tunnel has a designed length of 721 meters for the concealed section and 168 meters for the open-cut section, totaling 889 meters, and is excavated as a single-tube, one-direction drive. Its main works include portal works, open-cut section works, tunnel body excavation, advance support, surface grouting, primary support, secondary lining, and spoil ground protection.

Since entering the main tunnel of the Daxu Tunnel for construction on March 17, 2023, in response to poor surrounding rock of the mountain, complex geology, and high-quality construction process requirements, the construction party has overcome difficulties such as high tunnel construction risks, large temperature differences between day and night, high safety pressure, and a short effective construction period. It has organized construction in strict accordance with the principles of "weak blasting, short advance, strong support, early closure, frequent measurement, and timely secondary lining," strengthened monitoring and measurement and advanced geological forecasting, and managed explosives properly, thereby reducing safety risks.