Cutting through fault fracture zones, karst development areas, and micro-gas zones, and passing beneath the existing Shanghai-Kunming High-Speed Railway and Yinchuan-Kunming Expressway... On August 1, after more than 940 days and nights of arduous efforts by builders from China Railway No. 4 Engineering Group, the Luorongzhuang Tunnel on the Chongqing-Kunming High-Speed Railway—an important component of China's eight-vertical, eight-horizontal railway network—was safely holed through. It is reported that this is the first tunnel over 5 kilometers long to be holed through within Yunnan Province on the Chongqing-Kunming High-Speed Railway, laying the foundation for the opening and operation of the entire line.

Luorongzhuang Tunnel

The Luorongzhuang Tunnel is located in Songming County, Kunming City, Yunnan Province, with a total length of 5,260 meters. It is a single-tube, double-track tunnel that passes through a variety of complex geological conditions, including 4 fault fracture zones, 5 karst development sections, and 3 micro-gas sections. At the same time, the tunnel passes beneath the existing Shanghai-Kunming High-Speed Railway and Yinchuan-Kunming Expressway, with the shortest distances to the Shanghai-Kunming High-Speed Railway and Yinchuan-Kunming Expressway being only 20 meters and 10 meters, respectively. There are safety risks such as collapse and roof fall, mud and water inrush, harmful gas infiltration, and expressway settlement, making construction difficult and safety risks high. It is a key controlling project of the Kunming hub section of the Chongqing-Kunming High-Speed Railway.

Because the tunnel contains micro-gas, in order to prevent toxic gases such as gas from affecting the health of construction personnel, an automatic gas monitoring system was installed in the tunnel to monitor carbon monoxide, methane, and hydrogen sulfide content in real time, and gas monitoring personnel were arranged to monitor the gas concentration once every 4 hours, effectively ensuring construction safety. Intelligent systems such as personnel positioning, video monitoring, full-section 3D scanning, and emergency alarms were also installed in the tunnel, greatly improving the level of mechanization, informatization, and intelligence in the tunnel and using advanced technology to achieve efficient progress in tunnel construction.

Tunnel construction site

To ensure the safe and orderly progress of tunnel construction, the Central Yunnan Railway Construction Command of China Railway Kunming Group organized participating units, in light of actual site conditions, to study and optimize the construction organization plan. Based on the characteristics and difficulties of tunnel construction, special construction plans were prepared, risk control was continuously strengthened, process organization was optimized, and engineering measures such as controlled blasting, mechanical excavation, and high-precision advanced large pipe roofs were fully applied.

To effectively address the actual situation in which the relocation and modification of pipelines at the tunnel exit were difficult and constrained the construction schedule, after full technical demonstration, an inclined shaft was added 500 meters from the tunnel exit, increasing the original 4 working faces to 5, greatly improving construction efficiency and achieving the safe holing-through of the tunnel ahead of schedule.

Entrance of the inclined shaft of Luorongzhuang Tunnel

The Chongqing-Kunming High-Speed Railway is a key component of the Beijing-Kunming corridor of the national eight-vertical, eight-horizontal railway network, with a total length of 699 kilometers, of which the Yunnan section is 388.6 kilometers long. At present, 23 of the 63 tunnels in the Yunnan section of the Chongqing-Kunming High-Speed Railway have been holed through, and the construction of 10 key bridge and tunnel controlling projects is progressing smoothly. As the first high-speed railway in Yunnan Province designed for a speed of 350 kilometers per hour, after the entire line is completed and opened to traffic, the travel time from Chongqing to Kunming is expected to be shortened from the original 5 hours to as fast as about 2 hours.