China's homegrown largest-diameter tunnel-boring machine, Jinghua, successfully pierced through the west line tunnel of the Beijing East 6th Ring Road Reconstruction Project on June 28.
Designed by China Railway Siyuan Survey and Design Group Co., Ltd. and constructed by China Railway 14th Bureau Group Corporation Limited, both subsidiaries of China Railway Construction Corporation Limited, the tunnel is 7.4 kilometers long and is the longest highway shield tunnel in China.
The west line tunnel of the Beijing East Sixth Ring Road Reconstruction Project breaks through. [Photo/sasac.gov.cn]
The Beijing East Sixth Ring Road Reconstruction Project starts from the Beijing-Harbin Expressway in the south and ends at Luyuan North Street in the north. The total length of the line is about 16 kilometers, of which the shield tunneling method has been applied to a section of about 7.4 kilometers in length. Arranged in separate double holes, the diameter is 16.07 meters and the deepest section of the tunnel is approximately 75 meters underground. It is both the largest diameter tunnel adopting shield tunneling method under construction in northern China and the deepest underground tunnel in Beijing.
The stratum where the tunnel is located is a high-density, highly permeable sand layer, and passes through 55 risk sources, such as the Beijing-Harbin Railway, the Beijing Sub-Center Railway Station currently under construction, and multiple subways, highways, and rivers. Difficulties such as its super-large diameter, super-long distance, super-deep soil cover, and super-sensitive environment posed great challenges to the construction.
China Railway 14th Bureau Group Corporation Limited and China Railway Construction Heavy Industry Corporation Limited tailored a super-large-diameter shield tunneling machine, Jinghua, relying on their rich construction experience and parameter accumulation. The machine is equipped with more efficient fourth-generation atmospheric pressure tool changers, telescopic drive and other core technologies. Experts also gave suggestions on the tunnel's excavation to ensure that it would be completed at the fastest speed possible and with the least disturbance.
In addition, a smart management and control platform has been established that applies the Internet, BIM, and GIS technologies, successfully realizing digital management and the control of safety, quality, progress, and emergency security.
To control land subsidence, the grouting process is the key.
China Railway 14th Bureau Group Corporation Limited utilized super-large-diameter slurry shield tunneling synchronous double-fluid grouting technology, which shortened the grout consolidation time from the traditional 8 hours to 1 hour, providing a strong shield for the tunnel segment in a short time.
By using this technology, the project effectively controlled the uplift of the tunnel segment, and realized millimeter-level control of the ground subsidence.
The project's expert group, headed by Qian Qihu, an academician of the Chinese Academy of Engineering, agreed that this technology has filled the blank of synchronous double-fluid grouting for ultra-large diameter slurry shield tunneling in China.
Throughout construction, the builders overcame 11 technical problems, created a single-month excavation record of 542 meters for a shield tunneling machine with a diameter of 16 meters, and applied for 23 research and development methods and patents.
The Beijing East Sixth Ring Road Reconstruction Project is a landmark project that effectively improves the capital's urban space and solves the problem of highways dividing the city.
Planned to be completed and opened to traffic in 2024, it will improve Beijing's transportation services, promote the integration of transportation in the Beijing-Tianjin-Hebei region, and build a comprehensive transportation system.
(Executive editor: Xie Yunxiao)
