On October 22, with a blast, the right tube of Paomashan No. 1 Tunnel on the Kangding bypass section of the Ya'an–Yecheng National Expressway was holed through. This tunnel has the largest elevation difference between its entrance and exit in the world.

Paomashan No. 1 Tunnel is invested in by Shudao Group's Zanggao Yakang Company and constructed by Sichuan Road & Bridge Transportation Construction Group. It is located in Kangding City, Garzê Prefecture, Sichuan Province. The left tube is 8,865 meters long and the right tube is 8,780 meters long, with a maximum burial depth of 1,250 meters. The elevation difference between the tunnel entrance and exit reaches 220 meters, equivalent to the height of more than 70 stories.

The project's enormous entrance-exit elevation difference, its location in a frigid high-altitude region, and construction through multiple fault zones have posed huge challenges. To reduce the tunnel gradient, designers adopted a double-tube, two-way separated extra-long "S"-shaped curve design, involving three left-right turns with a cumulative turning of 341 degrees, keeping the longitudinal gradient within the limit values of expressway design specifications.

The tunnel entrance work area involves one-way excavation of up to 4,000 meters, presenting problems such as long ventilation distance, many bends, polluted air, and low air volume at the working face. To overcome this difficulty, gallery-type ventilation was adopted, greatly shortening the ventilation distance, improving ventilation efficiency, and improving the construction environment inside the tunnel. Advanced pressure-relief holes, smooth blasting, and a segmented pumping system were also used to solve the problem of water inflow in the tunnel, effectively safeguarding workers' safety.

Up to now, the tunnel works of the Kangding bypass section of the Ya'an–Yecheng Expressway have cumulatively completed 28,250 meters, or 88.1% of the progress. Among them, Paomashan No. 1 Tunnel has completed 17,393 meters in both directions, or 98.6%, with only 252 meters remaining. Both tubes are expected to be holed through in 2024.

The Kangding bypass section of the Ya'an–Yecheng Expressway is part of the Chengdu–Kangding–Tibet Expressway in the Sichuan Provincial Expressway Network Plan (2014–2030). Once completed, it will effectively divert transit traffic from Kangding's urban area, ease congestion pressure in the main urban area, and promote all-for-one tourism development. It is of positive significance for strengthening rapid connections between the Chengdu Plain and Tibetan-inhabited areas and enhancing emergency support capacity.