On June 15, 2023, the Dashan Tunnel of the Chongqing Yibin section of the Chongqing Kunming high-speed railway was successfully completed, laying a solid foundation for the timely completion and opening of the line.

Chongqing Kunming High speed Railway is an important part of Beijing–Kunming corridor, one of the main channels of China's eight vertical and eight horizontal high-speed railway network. The line starts from Chongqing West railway station, passes through Chongqing City, Sichuan Province, Guizhou Province and Yunnan Province, and connects to Kunming South railway station. The total length of the line is 699 kilometers. A total of 21 stations are planned to be set, with a design speed of 350 kilometers per hour.

Dashan Tunnel is located at the junction of Bishan District and Jiangjin District of Chongqing. It is the first long tunnel of Chongqing Kunming High speed Railway in Sichuan Chongqing Section. The tunnel has a total length of 3561 meters and is mainly composed of mudstone and sandstone. The rock mass is broken and the bonding between the rock layers is poor. At the same time, the tunnel passes through the Seven Zero Reservoir, making construction operations difficult and safety risks high.

In order to overcome the difficulties caused by unfavorable geological conditions and carry out safe and efficient construction, the construction unit adopts the principle of first support, then excavation, short footage, weak blasting, fast closure, and frequent measurement to carefully organize the construction. In the area where the Qiling Reservoir is penetrated, advanced horizontal drilling and geological radar methods are used to detect the geological situation in front of the tunnel, ensuring the safe and orderly progress of tunnel construction.

After the completion and operation of the Chongqing Kunming high-speed railway, the fastest running time of trains from Kunming to Chongqing will be shortened to about 3 hours, further improving the national comprehensive three-dimensional transportation network, enhancing the connection between the Chengdu Chongqing dual city economic circle and the central Yunnan region, greatly improving the travel conditions of the people along the line, and promoting high-quality economic and social development along the line. Editor/Xie Li