On January 14, CCTV reporters learned from China Railway Kunming Group that the Zhongshao Tunnel, the longest tunnel on the Mile-Mengzi Railway in Yunnan and an important part of the China-Vietnam international corridor, has been successfully holed through, laying the foundation for the entire line to be completed and opened to traffic as scheduled.

The Zhongshao Tunnel is located between the cities of Mile and Kaiyuan in Yunnan Province. The tunnel has a total length of 4,062 meters, including 3,990 meters of blind tunnel and 72 meters of open-cut tunnel, with a maximum burial depth of 132 meters and a minimum burial depth of 0.3 meters. The tunnel features strongly developed karst, with dense karst forms such as surface karst depressions and karst trenches, and the surrounding rock is fractured and poorly stable. In addition, the tunnel passes beneath villages and is close to an expressway, resulting in high safety risks and great difficulty in construction.

“In view of the tunnel’s sensitive environment, during construction we adopted measures such as ‘short advance, weak blasting, and strong support,’ and equipped five types of advanced tooling and equipment, including rock drilling jumbos and arch frame assembly machines. Through scientific organization and reasonable arrangement, and by closely monitoring the management and construction of key procedures, we greatly improved construction efficiency while ensuring safety and quality, overcame construction challenges such as shallow cover, large surface settlement, and large initial support deformation, and ensured that the tunnel was holed through as scheduled,” said Niu Ruiliang, chief engineer of the Mile-Mengzi Railway Project Department of China Railway 12th Bureau.

According to Peng Faxin, chief engineer of the Mile-Mengzi Railway Section Command of China Railway Kunming Group, the Mile-Mengzi Railway is a key project in China’s efforts to promote the domestic “large circulation” and serve the domestic and international “dual circulation.” At present, more than 8,000 builders are working intensively every day on tunnel excavation, bridge erection, and other work, and the overall construction progress is encouraging: 95% of subgrade earthwork has been completed, and the tunnel and bridge works have reached 86% and 93%, respectively.

The Mile-Mengzi Railway starts in the north at Mile Station on the Yunnan-Guangxi Railway, runs south through Mile City and Kaiyuan City, and ends at Mengzi City, the seat of Honghe Prefecture. The main line is about 107 kilometers long, with a designed target speed for passenger trains of 250 kilometers per hour. It connects with the Kunming-Hekou Railway, part of the China-Vietnam international corridor, and construction began in December 2018. Once completed and opened to traffic, Kunming and Mengzi will be reachable within two hours, and the line will become a convenient passenger transport corridor between the two major urban agglomerations of central Yunnan and southeastern Yunnan. It will help accelerate urbanization along the route, promote tourism resource development, and support poverty alleviation and prosperity in ethnic minority areas, providing strong transport capacity support for Yunnan’s development into China’s center radiating toward South and Southeast Asia.