After 305 days of intensive work, the Bamiaozui Tunnel on both bores of the Guangyuan–Mianyang section expansion project of the Beijing–Kunming Expressway was successfully holed through on May 30. The project is invested in by Sichuan Expressway Company under Shudao Group and constructed by China Railway No. 5 Engineering Group. The breakthrough came 47 days ahead of the original 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-bore, six-lane facility with separated left and right carriageways. The left bore is 786 m long with a maximum overburden of about 89 m, and the right bore is 783 m long with a maximum overburden of about 90 m. It is a soft-rock, large-cross-section tunnel with minor gas, constructed by single-direction excavation from the exit portal. The transport conditions in the construction area are poor, with village roads widened to serve as temporary construction access roads, and the site is far from the provincial highway. The rock strata are geologically unfavorable, making construction difficult and safety risks high.

During construction, the project adopted multiple measures to ensure the smooth breakthrough of both tunnel bores. First, by combining digital, information-based and refined management, a "smart construction site" management system was established. Video surveillance and toxic and harmful gas detection systems were 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 umbrella arches were adopted; a combined excavation method of the three-bench and two-bench methods was used; and research on low-binder, low-rebound high-performance concrete and shotcrete technology and equipment was applied to ensure construction progress. Third, the quality management system was continuously improved through pre-shift technical briefings, strengthened process management, strict implementation of the three-inspection system and the acceptance system for concealed works, and intensified patrol and on-site supervision, thereby strengthening quality oversight and ensuring that construction quality and safety meet specification requirements.

The smooth breakthrough of both bores of the Bamiaozui Tunnel 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 a modern comprehensive transport system in Sichuan Province, 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."