On January 12, the left inlet and right outlet of the Qinling Tiantai Mountain Tunnel on the Baoping Expressway were successively holed through. This is another major progress following the breakthrough of the left outlet on January 6, with the construction period more than 400 days ahead of schedule, marking a new breakthrough in the construction of the Qinling Tiantai Mountain Tunnel project. Up to now, a total of 12.8 kilometers (both tubes) of the Qinling Tiantai Mountain Highway Tunnel has been excavated, accounting for 82.3% of the total length of 15.56 kilometers (both tubes).

The Qinling Tiantai Mountain Tunnel has a total length of 15.56 kilometers, a net width of 14 meters, a net height of 5 meters, a design speed of 80 km/h, and is a dual six-lane tunnel. It is currently the world's largest under-construction highway tunnel. The construction plan for this tunnel is the "three shafts and four sections" method, with No. 1 inclined shaft, No. 2 vertical shaft, and No. 3 inclined shaft. Among them, No. 1 and No. 3 inclined shafts serve both ventilation and construction access. Four contractors have opened additional working faces through the inlet pilot tunnel, ventilation inclined shaft, and reverse excavation from the outlet to ensure rapid and efficient tunnel construction.

The left inlet is in Contract Section LJ-10 with a length of 3.493 kilometers. The terrain and geological conditions are complex, with unfavorable phenomena such as fault fracture zones, rock bursts, and sudden water inrushes, making construction difficult and risky. The construction task was completed 493 days ahead of the original schedule. The right outlet is in Contract Section LJ-13 with a length of 3.757 kilometers. Construction faced many difficulties such as difficult material transportation and high ecological and environmental protection requirements. The construction task was completed 400 days ahead of the original schedule.

The Baoping Expressway is a component section of the national expressway Yinkun Line (G85), and is also the expressway construction project with the largest scale, highest construction standards, and greatest construction difficulty among the expressways under construction in Shaanxi Province during the "13th Five-Year Plan" period. Once completed, the Baoping Expressway will become a major transportation corridor crossing the Qinling Mountains from north to south, achieving the full connection of the Yinkun Line within Shaanxi Province. It is of great significance for implementing the new round of Western Development and the "Belt and Road" strategy, improving the national expressway network, improving regional traffic conditions, promoting cooperation and exchange between the Guanzhong-Tianshui and Chengdu-Chongqing economic zones, advancing the construction of Baoji as a national comprehensive transportation hub, and vigorously developing the province's "three economies."