On December 23, the Luhongshan Tunnel, a key control project on the Luhongshan (Hunan-Hubei border) to Cili section of the national key project G59 Hohhot-Beihai Expressway, achieved smooth breakthrough on both tubes. The project is invested in, constructed and operated by China Railway Communications Investment Group and built by China Railway Sixth Group. This milestone laid a solid foundation for the node target of opening the whole Lu-Ci Expressway to traffic in 2024.

The Lu-Ci Expressway starts at Luhongshan at the border of Hunan and Hubei provinces and ends near Zhangjiashan, west of the Cili West Interchange of the Changde-Zhangjiajie Expressway, with a total length of about 80 kilometers. The Luhongshan Tunnel is located at the starting point of the expressway, with its entrance and exit respectively in Wufeng County of Hubei Province and Shimen County of Hunan Province. It is an extra-long tunnel running through Luhongshan at the Hunan-Hubei provincial border, with a total length of 4,445 meters. The tunnel adopts a separated double-tube structure, designed for two-way four-lane traffic at 80 km/h, with a maximum burial depth of about 670 meters. China Railway Sixth Group is responsible for the construction task of single-end excavation of 2,482 meters within Hunan Province.

The area where the Luhongshan Tunnel is located is a typical karst development region, dominated by shale and limestone, with various adverse geological conditions such as gas, karst, and mud and water inrush, and it is excavated from a single end, posing huge construction safety risks and schedule pressure. The adverse geology is represented by abundant karst development. During construction, a total of 13 karst caves of various sizes were encountered, among which a large karst cave is 68 meters wide laterally, about 46 meters deep, and about 60,000 cubic meters in volume. There is also the karst cave with the largest water inflow on the entire line, with peak tunnel water inflow during the rainy season reaching one million cubic meters per day, making construction difficult and safety risks extremely high. In addition, the tunnel portal is located in a valley, the construction site is narrow, and transportation is extremely inconvenient.

As an important part of the "seven vertical and seven horizontal" expressway network of Hunan Province, the Lu-Ci Expressway connects from north to south the Three Gorges of the Yangtze River, the Hupingshan Nature Reserve, and the World Natural Heritage Zhangjiajie. The completion and opening of the project are of great significance for driving tourism resource development along the route, enhancing the comprehensive transport capacity of the corridor between Hunan and Hubei provinces, promoting social and economic development in northwestern Hunan, and continuously consolidating the achievements of poverty alleviation.

Supplementary Information

The G59 Hohhot-Beihai Expressway (Hohhot to Beihai) is one of the north-south trunk lines of the national expressway network, with a total length of about 2,628 kilometers, passing through Inner Mongolia, Shanxi, Henan, Hubei, Hunan and Guangxi. The Hunan section of the Hohhot-Beihai Expressway is about 700 kilometers long, including the Luhongshan to Cili Expressway, the Changsha to Zhangjiajie Expressway (Cili West to Zhangjiajie East), the Zhangjiajie to Guanzhuang Expressway, the Guanzhuang to Xinhua Expressway, the Xinhua to Xinning Expressway, the Yongzhou to Xinning Qingjiang Bridge Expressway, the Yongzhou to Lingling Expressway, and the Lingling to Daoxian Expressway. Among them, the Lu-Ci Expressway is 79 kilometers long, designed for a speed of 100 km/h, with two-way four lanes, a total investment of 14.42 billion yuan, and is expected to open to traffic in 2024.