Two large tunnel boring machines (TBMs) have now made breakthroughs on major project in China. The TBMs feature diameters of 15m and have been manufactured by China Railway Construction Heavy Industry Corporation Limited (CRCHI)
The TBM named Xingsheng has been used for the Xiangya Road crossing under the Xian Jiang River in Changsha City in Hunan Province. Meanwhile, the TBM named Zhenxing has completed its drive for the left lanes of Hengqin Mangzhou Tunnel in Zhuhai City, some 800km away from Changsha.
In Changsha the twin tubes measure 1,429m in length for the left lanes and 1,425m in length for the right lanes. Boring work for these drives commenced in March 2021. This will be the largest river-crossing tunnel in Hunan Province when complete. The Xiangya Road river-crossing tunnel is a key infrastructure project of Hunan Province, as well as for Changsha City, the provincial capital.
The project mainly crosses through moderately weathered rock and slightly weathered slate. The maximum strength extends to 86.6MPa. There are multiple fracture zones in this section, of which maximum depth reaches to 46.3m. At the same time, the Changsha Metro Line 6 was under construction in parallel, bringing more challenges and risks to construction.
CRCHI customised the Xingsheng TBM for the project. The cutters were designed to reduce impact during tunnelling in the rock and composite strata under the river. This reduced the frequency of cutter replacement and improved the excavation efficiency.
Just a few days earlier, the TBM named Zhenxing had completed its drive for the Hengqin Mangzhou Tunnel, having started work in mid-2022. This project is located in Guangdong-Macao Deep Cooperation Zone. The tunnel is about 3km long and is planned to open to traffic in 2024. The tunnel runs under the Maliuzhou Waterway, connecting Hengqin Island in the south and Zhuhai City in the north. The whole tunnel crossed through the ultra-soft soil layer, with the condition of more than 74.7% of the ultra-fine particles less than 20 microns, and the maximum depth is 50m. It is currently the super-large diameter shield machine subsea tunnel with the softest stratum and the highest content of fine particles in China.