On September 22, the import parallel adit of the Yiliang Tunnel on the Chongqing-Kunming High-Speed Railway—currently the high-speed rail branch tunnel under construction in China with the highest design speed and the longest mileage—was safely holed through, marking the completion of all auxiliary tunnel construction and the full entry into the main tunnel construction stage. With this, the Yunnan section of the Chongqing-Kunming High-Speed Railway has fully entered the main construction stage, and the construction of seven key and difficult control projects is progressing smoothly.

The Yiliang Tunnel is located in Zhaotong City, Yunnan Province, spanning the border of Yanjin and Yiliang counties. With a total length of 24.8 kilometers, it is a double-tube single-track tunnel and is currently the longest high-speed rail tunnel under construction in China designed for a speed of 350 kilometers per hour, as well as a key control project of the entire line. The import parallel adit holed through this time has a total length of 1,591 meters; its safe breakthrough has laid a solid foundation for realizing the "long tunnel excavated from short adits" approach—on the one hand, it verifies geological conditions and adds excavation faces for the main tunnel, and on the other hand, it enhances tunnel ventilation and improves the construction environment. It will be permanently retained as a drainage adit after the railway is put into operation. According to reports, all 54 tunnels and 91 bridges in the Yunnan section of the Chongqing-Kunming High-Speed Railway have now started construction, and the seven key bridge and tunnel control projects are progressing smoothly.

The Chongqing-Kunming High-Speed Railway is an important component of the Beijing-Kunming corridor of the national "Eight Vertical and Eight Horizontal" railway network. With a total length of 699 kilometers, of which the Yunnan section is 388.6 kilometers long, it is the first high-speed railway in Yunnan Province with a target passenger train speed of 350 kilometers per hour, and its bridge-to-tunnel ratio is as high as 87.4%. Once the entire line is completed and opened to traffic, it will run through Yunnan, Guizhou, Sichuan, Chongqing and other provinces and municipalities, becoming a convenient major corridor for Southwest China's opening-up and for the Belt and Road Initiative to reach ASEAN. It is of great significance for promoting high-quality regional economic development, driving resource development and industrial growth, and boosting rural revitalization and ethnic unity and progress.