On the morning of October 23, at the construction site of the Shuan Tunnel along the Chengdu-Chongqing High-Speed Railway, the safety installation of the cutter head for the “Chengyu” tunnel boring machine (TBM) was successfully completed. This pivotal moment signifies that the tunneling operation using the “Chengyu” TBM is now in its final countdown phase.
The Chengdu-Chongqing rail line is a crucial part of China’s “eight vertical and eight horizontal” high-speed rail network, particularly serving the river corridor. Spanning a total length of 292 kilometers, it begins at the Chongqing North Station and travels through several districts in Chongqing before reaching Chengdu. The trains on this line are designed to operate at speeds of up to 350 kilometers per hour.
The Shuan Tunnel itself stretches 10,380 meters and utilizes both “tunnel boring” and “open-cut” construction methods. The boring section measures 9,824 meters and employs two tunnel boring machines, the “Shuan” and “Chengyu.” While the “Shuan” machine has already begun tunneling, it was the “Chengyu” that had its cutter head recently installed.
According to Jia Cheng, the head of the TBM team for China Railway 11 Bureau’s Chengdu-Chongqing project, the “Chengyu” tunnel boring machine features a boring diameter of 14 meters, weighs an impressive 3,344 tons, and has a total power output of 10,000 kilowatts. It utilizes an integrated and modular design to tackle the challenges associated with launching a large-diameter TBM. The machine is equipped with advanced technology, including a pressurized composite cutter head, telescopic main drive, and retractable cameras within the cutting chamber for improved monitoring.
The installation of the cutter head is recognized as the most challenging and hazardous step in the entire assembly process of the TBM. The 14-meter-diameter cutter head, which weighs approximately 415 tons, is constructed from a middle section and four segments that were assembled and welded at ground level. Its design features artistic elements, such as the Sun God Bird, symbolic of vitality and aspiration for a better life.
Once the cutter head is lowered, the TBM will proceed with advancing the shield, managing the tail of the machine, connecting pipelines, and conducting synchronized testing, with tunneling operations expected to commence by early December.
Wang Xuesheng, commander of the construction headquarters for the Chengdu-Chongqing line at the Yangtze River Railway Group, highlighted the complexity of the geological conditions, which predominantly consist of mudstone and gravel layers. To address these challenges, several innovative technologies have been implemented, including a synchronized pushing system for the TBM, intelligent tunneling management, and a multi-level grouting system. These advancements aim to enhance construction efficiency while minimizing risks and ensuring the safety of nearby sensitive structures throughout the tunneling process.
