By Lynda Myer
As the largest metro investment in China, construction process of the Guangzhou Metro Line 18/22 has attracted much attention. Designing the 52 φ8.8m EPB/Slurry TBMs for this project and creating the world record of the largest TBM construction group applied in a single project, CRCHI helps the construction of Guangzhou Metro and serves the Guangdong-Hong Kong-Macao Greater Bay Area.
Being known as the geological museum, an unique geological fault structure belongs to Guangzhou that is placed in the alluvial plain of the Pearl River Delta. The metro project is spread all over this city and 33 comprehensive hubs reach 7 districts. Considering that the path of project includes the soft rock and hard rock alternate as well as the silt layer with high water content and low bearing capacity, which is very easy to cause ground settlement, the equipment crosses the area with high safety risk and great construction difficulty.
Passing through Nansha, Panyu, Haizhu, Tianhe and Liwan districts, the Guangzhou Metro Lines 18/22 has a total length of 91.3 km and is China’s first high-specification metro line with a speed of 160 km/h. While the total length of Line 18 is 62.7 km, the whole of Line 22 is 31 km. The project is large in scale, tight in construction period, high in standard, difficult in construction, wide in application of new technologies and large in equipment investment. The general contractor of the construction project is up to China Railway Construction South China Construction Co., Ltd. The commencing date of this project was on Nov 30, 2017. whereas the first φ8.8 m TBM was commissioned on Aug 29, 2018.
The route of successively crossing for 52 TBMs of CRCHI is beneath rivers, operating metro lines, residential area and other risky areas. The vertical clear distance between the working tunnel and the existing operating tunnel is only 5.5 meters, and there are 11 rivers with a width of more than 200 meters and a maximum length of 1600 meters.
The fourth generation of φ8.8m TBM has been presented for the project by CRCHI in order to solving the engineering geological problems. Including frozen cutter head, retractable main drive, cutters state monitoring mode, a number of technologies were developed and designed, while in order to providing a strong guarantee for the rapid, efficient, safe and environmental protection construction of the tunnel with the world’s largest 52 TBMs group, a professional technical service team of 200 people was dispatched.
Encountering different ground layers such as soft rock, hard rock and soft & hard alternating in the process of tunneling by the TBM, the problem of tunnel collapse is overcoming by the TBM adopt with the frozen cutter head technology, which can freeze the soil layer into a shell type safety body, just like customizing a suitable safety helmet for the machine, which is more convenient for tunneling while stabilizing the surrounding geological environment.
In extremely hard rock and high-risk environments, the telescopic main drive technology can help the cutter head to retreat, leaving more space for maintenance personnel to change cutters. At the same time, in cooperation with the cutters status monitoring mode, the status of the ‘teeth’ of the TBM is monitored in real time, and the best replacement time is selected, so as to minimize the construction risk.
Inauguration of the first section of Guangzhou Metro Line 18 was officially done on September 28, 2021. Reducing the direct access time between the main city of Guangzhou and the Nansha Free Trade Zone to just 30-minute, during the trial operation this project set the world’s fastest metro operation record of 176 km/h. Achieving to the world’s third rank and making the total mileage of Guangzhou Metro 600 kilometers, on March 31, 2022, the first section of Guangzhou Metro Line 22 was officially opened. The first breakthrough section of Guangzhou Metro Line 18/22 reach 75 km.
Following completion of all the tunnel, the 52 TBMs of CRCHI will be put into other projects after maintenance and refurbishment.
For more details, please watch the video below.
