By Lynda Myer
In order to completing the right line tunneling of the Xiangya Road river-crossing tunnel in Changsha City, the largest slurry TBM in China’s Hunan Province broke through on March 12th 2023. As the largest diameter shield machine tunnel in Hunan Province, this TBM has achieved a twin-tunnel break through. Been commissioned back on 30 March 2021, the slurry TBM Xingsheng with 15.01m length has been manufactured by the China Railway Construction Heavy Industry Corporation Limited (CRCHI).
The Xiangya Road river-crossing tunnel is the largest river-crossing tunnel in Hunan Province by far and is considered a key infrastructure project for Hunan Province, as well as a major project to raise commerce in Changsha City, which is the provincial capital. With the whole length of 4180m, the left line TBM tunnel is 1429 meters long, and 1425 meters belongs to the right line TBM tunnel. While this project is the first two-way six-lane river-crossing tunnel in Changsha, the scheduled date for inauguration of the main line is end of 2023.
With path geology of moderately weathered rock and slightly weathered slate, the maximum strength extends to 86.6 MPa and there are multiple fracture zones in this section, of which the maximum depth reaches down to 46.3m. Additionally, building of the Changsha Metro Line 6 causes more challenges and risks to the construction.
As a result of the geological conditions, CRCHI customized the 15.01m Xingsheng TBM. The cutters were designed specifically to effectively reduce the impact upon the cutter head during the tunneling in the rock and composite strata under the river. The frequency of the cutters replacement was reduced which improved the excavation efficiency.
Advance in Hengqin Mangzhou Tunnel
The slurry TBM Zhenxing with 15.01m super-large diameter commenced its journey on the left line of Hengqin Mangzhou Tunnel in Zhuhai City, which is 800km away from Changsha on March 9th 2023. The CRCHI was manufacturing company of this machine too and it was launched on July 15th, 2022.
With around 3 km long, the Hengqin Mangzhou Tunnel is located in Guangdong-Macao Deep Cooperation Zone and it is planned to be opened to traffic in 2024. Linking Hengqin Island in the south and Zhuhai City in the north, the tunnel crosses beneath the Maliuzhou Waterway. The crossing route of this tunnel is an ultra-soft soil layer, where over than 74.7% of the ultra-fine particles were less than 20 microns, and the maximum depth was 50m. It is currently the only super-large diameter shield machine working in such conditions – a subsea tunnel, softest stratum and the highest content of fine particles in China.
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