On Mar 12th the largest slurry TBM in use in China’s Hunan Province broke through, marking completion of the second tube of the Xiangya Road river-crossing twin-tunnels in Changsha City.
The 15.01m slurry TBM ‘Xingsheng’ was manufactured by China Railway Construction Heavy Industry Corporation Limited (CRCHI) and launched on Mar 30,2021. As the largest river-crossing tunnel in Hunan Province, the Xiangya Road river-crossing tunnel is considered a key infrastructure project not just for the Province, but also for Changsha City, the provincial capital. The total length of the tunnel is 4180m. The left line TBM tunnel is 1429m long, and the right line TBM tunnel 1425m long. It is the first two-way six-lane river-crossing tunnel in the city and will open to traffic by the end of 2023.
The project traversed moderately weathered rock and slightly weathered slate with a maximum strength of 86.6MPa. There are multiple fracture zones through this section, with a maximum depth of 46.3m. A further challenge was the concurrent parallel construction of the Changsha Metro Line 6.
As per the geological conditions, CRCHI customized the 15.01m ‘Xingsheng’ TBM with cutters designed specifically to reduce the impact on the cutter head during tunnelling through the rock and composite strata under the river. According to CRCHI this greatly optimized the required frequency of cutter replacements and improved excavation efficiency.
On March 9th, the 15.01m diameter slurry TBM ‘Zhenxing’ broke through the left tube of the Hengqin Mangzhou Tunnel in Zhuhai City, some 800km from Changsha. The TBM was manufactured by CRCHI and was launched on July 15th 2022.
The Hengqin Mangzhou Tunnel is located in the Guangdong-Macao Deep Cooperation Zone. At 3km long the tunnel is slated to be open to traffic in 2024. The tunnels cross beneath the Maliuzhou Waterway, connecting Hengqin Island in the south and Zhuhai City in the north. Ground conditions include ultra-soft soil layers, with more than 74.7% ultra-fine particles of less than 20 microns, and a maximum depth of 50m.