On May 30, after 305 days of intensive work, the Bamiaozui Tunnel on the Guangyuan–Mianyang expansion section of the Beijing–Kunming Expressway was successfully holed through on both tubes, 47 days ahead of the owner's planned schedule, laying a solid foundation for the full completion and opening of the project.

The Bamiaozui Tunnel is located in Jiange County, Guangyuan City. It is designed as a dual-tube, six-lane split carriageway, with the left tube 786 m long and a maximum overburden of about 89 m, and the right tube 783 m long with a maximum overburden of about 90 m. It is a soft-rock, large-section tunnel with minor gas, constructed by single-direction excavation from the exit portal. The transport conditions in the tunnel construction area are poor, with widened village roads basically used as temporary access roads, and the site is far from the provincial highway; the rock strata are poor, construction is difficult, and safety risks are high.

During construction, the project adopted multiple measures to ensure the smooth holing-through of both tubes. First, by combining digital, information-based and refined management, a "smart construction site" management system was established, with video monitoring and toxic and harmful gas detection systems installed in the tunnel to display information on each construction process in real time, comprehensively identify safety hazards, improve ventilation and disaster prevention and relief systems, and formulate relevant emergency plans, thereby achieving all-round management. Second, for sections with poor geological conditions, various auxiliary engineering measures such as advanced pre-reinforcement and arch lagging were adopted, combined three-bench and two-bench excavation methods were used, and low-binder, low-rebound high-performance concrete and shotcrete technology and equipment were studied and applied to ensure construction progress. Third, the quality management system was continuously improved; through pre-shift technical briefings, process management was strengthened, the three-inspection system and the acceptance system for concealed works were strictly implemented, inspection and side-station supervision were intensified, and quality supervision was reinforced to ensure that construction quality and safety meet specification requirements.

The smooth holing-through of both tubes of the Bamiaozui Tunnel this time has pressed the "accelerator" for the opening of the entire Guangyuan–Mianyang Expressway under construction. Once the project is fully completed and opened to traffic, it will accelerate the pace of building Sichuan Province's modern comprehensive transport system, complete the construction of a major regional transport corridor, promote balanced regional development, and help foster a new development pattern of "one mainstay and multiple pillars".