On June 17, the "Jingbin Tongxin" shield machine, the largest-diameter shield machine for railways in the Beijing-Tianjin-Hebei region, successfully passed beneath the last major risk source—the Limingzhuang Depot of Tianjin Metro Line 2. The underpass section is about 600 meters long, laying a strong foundation for the subsequent smooth breakthrough of the shield tunneling.

The "Jingbin Tongxin" shield machine in operation

The shield-driven section of Tunnel No. 1 at Tianjin Airport on the Beijing-Binhai Intercity Railway is 2,923 meters long with a maximum burial depth of 29.82 meters, constructed using the 13.8-meter large-diameter slurry balance shield machine "Jingbin Tongxin." Since its launch last December, the shield machine has successively passed beneath major risk sources including the Beijing-Tianjin-Tanggu Expressway, Jinhang Highway, Beitang Sewage River, and the Limingzhuang Depot of Metro Line 2.

The long-distance underpass of the shield machine beneath the metro depot imposes extremely stringent requirements on surface settlement and carries extremely high safety risks; it is the first such case in China. To ensure the safe operation of the shield machine, the project team joined forces with research institutes to carry out technological innovation and technical research on intelligent shield tunneling, simultaneous dual-fluid grouting, intelligent monitoring and analysis, and intelligent slurry treatment, effectively safeguarding the underpass work.

The Limingzhuang Depot has a total of 30 train tracks, making settlement extremely difficult to control. During tunneling, the project team used self-developed high-viscosity plastic anti-settlement mud materials, simultaneous dual-fluid grouting, and intelligent systems such as intelligent slurry circulation control, significantly improving tunnel axis accuracy and greatly reducing surface settlement; autonomous cruising of the shield has now been achieved. According to automated monitoring feedback, surface deformation has consistently been controlled within ±2 millimeters, and no monitoring alarms were triggered during the crossing, achieving a micro-disturbance, imperceptible underpass.

According to reports, Tunnel No. 1 at Tianjin Airport is a throat project of the Beijing-Binhai Intercity Railway. During shield tunneling, it is necessary to traverse silty clay strata, silty sand layers, and confined water aquifers over long distances, with frequent stratum changes in the tunneling area. The "Jingbin Tongxin" shield machine is equipped with a self-developed automatic guidance and measurement system and a tunneling management system, with an automatic guidance angular accuracy of 1 second and a measurement distance of no less than 200 meters, capable of controlling the tunneling direction error within ±3 millimeters. It is equipped with the unique long-distance tunneling without cutter replacement technology for super-large-diameter shield machines, enabling no cutter replacement throughout the entire tunneling of the project. At the same time, the shield machine is also equipped with cutterhead cleaning and injection devices to avoid mud cake formation during tunneling. A series of technological measures have ensured tunnel tunneling efficiency. At present, the tunnel shield has advanced 703 rings, about 1,406 meters, accounting for 48% of the total mileage, and is expected to complete reception by the end of December.

Completed tunnel

The Beijing-Binhai Intercity Railway is a key railway project to promote the integrated development of transportation in the Beijing-Tianjin-Hebei region, and is also a concrete practice of implementing the major national strategy of coordinated development of Beijing-Tianjin-Hebei. The first-phase project, the Baodi to Beichen District section, was completed in December 2022. The second-phase project starts from Beichen Station, passes through Binhai Airport, and connects to Binhai West Station. As the third high-speed railway corridor connecting Beijing and Tianjin, once the entire Beijing-Binhai Intercity Railway is completed, it will take only about one hour to travel directly from Tongzhou in Beijing to Tianjin Binhai New Area.

At the same time, once the entire Beijing-Binhai Intercity Railway is open to traffic, it will connect with the Beijing-Tangshan Intercity Railway, Beijing-Tianjin Intercity Railway, Tianjin-Qinhuangdao High-Speed Railway, and Tianjin-Baoding High-Speed Railway, forming a large comprehensive transportation hub at Tianjin Binhai Airport integrating railway, civil aviation, metro, and other modes of transportation. This will further improve the regional road network structure of the Beijing-Tianjin-Hebei region, provide more convenient and efficient travel services for the people of the three regions, and boost the integrated development of the regional economy.