On February 20, the ninth day of the first lunar month, the first blast of the Year of the Ox construction on the Kangding Bypass section of the Sichuan Ya'an to Xinjiang Yecheng Expressway (Ya-Ye Expressway) echoed in the left tube of Paomashan No. 1 Tunnel. The elevation difference between the portals of Paomashan No. 1 Tunnel reaches 222 meters, equivalent to an 80-story building, making it the tunnel with the world's largest elevation difference between portals. The tunnel is expected to break through by the end of 2021, and the Kangding Bypass section of the Ya-Ye Expressway is expected to be completed and open to traffic in 2022, seamlessly connecting with the Ya'an-Kangding Expressway after opening.

　　Early Resumption

　　To Make Up for Construction Progress

　　The Kangding Bypass section is a component of the Ya-Ye Expressway and also a component of the Chengdu-Kangding-Tibet Expressway. The entire line is designed for a speed of 80 kilometers per hour, built to a two-way four-lane standard, with a construction period of 4 years. The project is invested and constructed by Sichuan Communications Investment Group's Tibetan Plateau Ya'an-Kangding Company, with an estimated investment of 3.6 billion yuan, averaging about 200 million yuan per kilometer.

　　The Kangding Bypass section of the Ya-Ye Expressway has 2 interchanges, 1 service area, and 1 parking area, with the service area and parking area co-located with the interchanges. Among them, the two extra-long tunnels, Paomashan No. 1 and No. 2 (with a combined length of 15 kilometers), are the key and difficult projects of the entire line.

　　On February 20, deep inside the Paomashan Tunnel in Kangding, LED lights illuminated the approximately 10-meter-high construction trolley, and 9 workers stood on the "grid compartments" holding pneumatic drills and pushing forward, as the hard rock layer shattered bit by bit and a "subway-style" expressway extended forward. It is reported that most workers entered the site on the sixth day of the first lunar month (February 17), and personnel and equipment have been added on site.

　　Wei Hongbin, deputy manager of the Kangxin K1-1 project of Sichuan Communications Construction Engineering Co., Ltd., explained that the reason for starting work so early this year was to make up for the progress affected by the epidemic last year and to overcome the worldwide challenges faced in tunnel construction as soon as possible.

　　World Record: Portal Elevation Difference of "80 Stories"

　　The "worldwide challenge" mentioned by Wei Hongbin occurs during the construction of Paomashan No. 1 Tunnel on the Kangding Bypass section of the Ya-Ye Expressway. The tunnel has a designed length of 8,780 meters, yet the elevation difference between its portals reaches 222 meters, the largest among expressway tunnels in the world.

　　"222 meters is equivalent to an 80-story building. If the route from the entrance to the exit were entirely straight, the gradient would simply not meet expressway driving requirements, so a bend was specifically designed—this is a deliberately lengthened tunnel," said Wei Hongbin, who has extensive experience in plateau highway construction but was still astonished by the tunnel's design. "Paomashan No. 2 Tunnel is also a project with a short-distance elevation rise; after a bend was designed, Tunnels No. 1 and No. 2 happen to form an S shape. This is the first time I have participated in such a project."

　　Speaking of tunnel excavation, Li Jinyong, chief engineer at the Paomashan Tunnel entrance site, believes that the emergencies encountered during construction are the real difficulties. "Rock bursts, water inflow, fault zones, large deformation due to biased pressure, unexpected gas emissions... The geological conditions in this area are extremely complex, leading to many emergencies. Fortunately, we had comprehensive contingency plans in place, which ensured the safety of construction personnel," he said.

　　Nearly Half of the Work Completed, Breakthrough Expected Within the Year

　　According to Wei Hongbin, as of now, about 50% of the work on Paomashan No. 1 Tunnel and the bridges connected to it has been completed. This year, the project department will take measures such as reverse excavation from the ventilation adit working point, adding working faces, and increasing personnel and equipment input to comprehensively accelerate construction progress, striving to achieve tunnel breakthrough by the end of the year.

　　While Paomashan No. 1 Tunnel continues to extend, other component projects of the Kangding Bypass section of the Ya-Ye Expressway are also under accelerated construction. At the Shenghang Extra-Large Bridge construction site, dump trucks and mixer trucks shuttle back and forth; inside Paomashan No. 2 Tunnel, loud blasts are heard, and transport vehicles methodically carry away the muck.

　　It is reported that the 17.8-kilometer Kangding Bypass section of the Ya-Ye Expressway is expected to open to traffic across the entire line in 2022. This expressway, with a bridge-tunnel ratio as high as 94%, will seamlessly connect with the Ya'an-Kangding Expressway.