On January 18, the Paomashan No. 1 Tunnel, the largest single tunnel with an elevation difference of 220 meters, achieved twin-bore breakthrough on the Sichuan Kangding Bypass Section of the Sichuan Ya'an to Xinjiang Yecheng Expressway (hereinafter referred to as the "Kangding Bypass Section of the Ya-Ye Expressway"), laying a solid foundation for the full breakthrough of the entire Kangding Bypass Section.

　　The Paomashan No. 1 Tunnel on the Kangding Bypass Section of the Ya-Ye Expressway is invested in by Sichuan Tibetan-Highway Ya-Kang Company of Shudao Group and constructed by Sichuan Road & Bridge Transportation Construction Group. Located in Kangding City, Ganzi Prefecture, Sichuan Province, the tunnel has a left bore length of 8,865 meters and a right bore length of 8,780 meters, and is a double-bore, two-way separated extra-long "S"-shaped curved tunnel. It is 46.4 meters longer than the completed Liangwangshan Tunnel on the Fuyi Expressway in Yunnan, making it the world's expressway single tunnel with the largest entrance-exit elevation difference. The tunnel entrance is at an altitude of 2,388 meters and the exit at 2,608 meters, with an elevation difference equivalent to the height of an 80-story building.

　　The Paomashan No. 1 Tunnel is located in the transition zone between the Sichuan Basin and the Western Sichuan Plateau, a typical area with high altitude, severe cold, and high seismic intensity. It crosses the Longmenshan and Xianshuihe fault zones, with seismic intensity reaching Grade IX, extremely complex geological conditions, and extremely high construction difficulty. The maximum buried depth of the tunnel reaches 1,250 meters, resulting in high in-situ stress in the rock mass and large variations in lithology. Rockburst zones account for 51% of the tunnel, and a total of 425 rockbursts of various sizes have occurred since construction began. Water inflow is severe in some construction areas, with a maximum daily inflow of 12,500 cubic meters, equivalent to the water volume of 28 standard indoor swimming pools.

　　The Kangding Bypass Section of the Ya-Ye Expressway is a component of the Chengdu-Kangding-Tibet Expressway in the "Sichuan Provincial Expressway Network Plan (2014-2030)". The project starts at Kangding Interchange in Shenghang Village, Lucheng Subdistrict, Kangding City, connects with the Ya-Kang Expressway, and ends at Daping Village, Yulin Subdistrict. The project consists of Paomashan No. 1 Tunnel, Paomashan No. 2 Tunnel, and Paomashan Bridge, with a bridge-tunnel ratio as high as 92.95%, making it one of the expressways with the highest bridge-tunnel ratio and the greatest construction difficulty in Sichuan and even the whole country. During construction, it is constrained by the "Seven Extremes, Three Highs, and Two Larges" conditions. The "Seven Extremes" are ultra-complex alignment, ultra-large turning, ultra-large elevation difference, ultra-large dislocation, ultra-high intensity, ultra-long expressway tunnel group, and ultra-high-frequency rockbursts; the "Three Highs" are high altitude, severe cold, and high in-situ stress; and the "Two Larges" are large external interference factors from the overall construction of the bypass section passing through the urban area, and multiple crossings of strong water-rich zones with large daily water inflow.

　　At present, 96% of the tunnel excavation has been completed on the Kangding Bypass Section of the Ya-Ye Expressway project, 100% of the bridge substructure and 100% of the superstructure have been completed, and 80% of the roadbed works have been completed. After the project is completed, driving from Kangding urban area to Xinduqiao will save more than one hour, and it will effectively divert transit traffic from Kangding urban area and ease congestion pressure in the main urban area.