Recently, the Tongshan Tunnel left and right tubes of the TTWA-LJ07 section subgrade project on the Wuwei–Anqing section of the Tian-Tian Expressway successfully broke through one after another, making it the **tunnel on the entire Tian-Tian Expressway line to achieve double-tube breakthrough. As a controlling node project, the double-tube breakthrough of Tongshan Tunnel marks a major milestone in the project's construction and provides solid assurance for the full opening of the Tian-Tian Expressway.

Tongshan Tunnel is located in Jinshe Township, Zongyang County, Tongling City, Anhui Province. It is designed as a separated tunnel with the same width as the subgrade; the clear width of a single tube is 13.75 m, and each tube has three lanes. The left tube is 462 m long and the right tube is 456 m long, with a burial depth of approximately 3.5 m to 97 m. The tunnel passes mainly through residual slope deposits and moderately weathered tuffaceous breccia. The residual slope deposit layer is relatively thin and the geological conditions are poor, making construction difficult and posing a great test to the project's organization and management capabilities and safety control level.

To ensure the overall construction schedule of Tongshan Tunnel, the project team planned ahead, organized meticulously, and continuously optimized construction techniques. Based on the geological conditions and actual site conditions, the team actively coordinated with the owner and the design unit and conducted multiple on-site surveys. The excavation sequence for Class V surrounding rock was changed from the CD method to the three-bench method, and the excavation sequence for Class IV surrounding rock with reserved core soil was changed from ring excavation to the two-bench method. The principles of "advanced pipe forepoling, strict grouting, short advance, strong support, rapid closure, and frequent measurement" were strictly followed, which improved excavation efficiency, accelerated the conversion of construction process cycles, and shortened the construction period while ensuring construction safety.

Facing severe challenges such as high temperatures and heat, as well as flood prevention and control, all members of the project team stood firm and rose to the difficulties. After more than 150 days and nights of arduous work, they successfully achieved the goal of timely double-tube breakthrough of the tunnel, making it the **tunnel on the entire line to break through in both directions. This has accumulated rich experience for the project's subsequent construction and represents a major step toward the goal of opening to traffic.

As an important part of the northern riverside expressway in Anhui Province, the Tian-Tian Expressway is of great significance for strengthening Anhui's connections with the Yangtze River Delta region and promoting regional economic development.