Recently, the Dechang Tunnel on the Chengdu-Kunming Railway double-track line, constructed by China Railway 11th Bureau Group, was successfully holed through, marking the completion of all 25 tunnels along the Mianning-Miyi section of the Chengdu-Kunming Railway capacity expansion project.

The Dechang Tunnel is located in Dechang County, Liangshan Prefecture, on the section between Dechang Station and Miyi Station. With a total length of 14,365 meters and a maximum burial depth of about 1,000 meters, it is a double-track tunnel and a major, high-risk project along the entire line. The tunnel has two inclined shafts and one parallel drift, providing a total of seven working faces. The tunnel passes through unfavorable geological conditions such as high-pressure water-rich zones, fault fracture zones, high in-situ stress, and high geothermal heat, posing extremely high challenges to construction technology. At 8:18 on the 21st, with the successful completion of the final blast at the Dechang Tunnel site, construction workers from both ends of the tunnel met inside the tunnel.

The Chengdu-Kunming Railway capacity expansion project is a key construction project of the national Western Development Program, with a total length of 623.339 kilometers. The Chengdu-Emei section is 128.698 kilometers long and opened at the end of December 2017; the Miyi-Panzhihua section is 108.307 kilometers long and opened at the end of May 2020. Currently, only the 156-kilometer Mianning-Miyi section and the 230-kilometer Mianning-Emei section remain. These two sections are the most difficult to build and the longest in the Chengdu-Kunming Railway capacity expansion project. The Mianning-Miyi section alone has 95 bridges and 25 tunnels, with a bridge-tunnel ratio of 63%. At present, all 25 tunnels in the Mianning-Miyi section have been holed through, and the subgrade and bridge works are basically complete.