Shanghai Airport Link Line Large-Diameter Shield Tunnel Breakthrough in Soft Soil Strata, Shield Tail Brush Ensures Safe Long-Distance Shield Tunneling

Shanghai Airport Link Line, an important transportation infrastructure project in Shanghai, plays a significant role in connecting Hongqiao Hub and Pudong Airport and optimizing the city's comprehensive transportation network. Recently, the shield tunnel section between Hongqiao Station and Qibao Station was successfully completed. Located in Shanghai's typical coastal soft soil strata with high groundwater level, weak soil bearing capacity, and densely distributed buildings, the long-distance continuous tunneling placed extremely high demands on the stability of the shield tail sealing system. As a critical sealing component of the shield machine, the shield tail brush served as an important safeguard, effectively preventing slurry backflow, water leakage, and sediment intrusion, ensuring safe, leak-free, and highly efficient long-distance tunneling.

The shield tunnel section has a total length of 2,782 meters and was driven by a 14.07-meter-diameter large-diameter slurry shield machine, with tunnel burial depth ranging from 16 to 32 meters. The excavation route mainly passed through weak strata including silty clay, silty clay, and sandy silt. The groundwater level is close to the surface and the soil permeability is high, creating potential risks such as slurry backflow, segment leakage, stratum settlement, and surface cracking. For large-diameter shield machines, the annular gap between the shield body and segments is larger, so the shield tail brush acts as the final physical barrier preventing external groundwater and sediment from entering the shield body.

Through a multi-layer steel wire brush structure, the shield tail brush closely contacts the outer surface of tunnel segments to form a sealed grease chamber. By continuously injecting shield grease, stable sealing pressure is maintained to effectively block groundwater, sediment, and simultaneous grouting slurry intrusion. If the wear resistance of the shield tail brush is insufficient, installation accuracy is not properly controlled, or grease supply is interrupted, sealing performance may be affected, leading to equipment shutdown, brush replacement, and ground disturbance, which could significantly impact construction safety and progress.

To overcome the challenges brought by soft soil layer excavation, the project team optimized the shield construction plan according to geological characteristics. During the selection of sealing components, multi-layer steel wire composite shield tail brush products with excellent wear resistance, pressure resistance, and long-distance tunneling adaptability were selected, paired with a dedicated shield sealing grease system. Before construction, strict inspections were carried out on product quality, incoming inspection, dimensional re-measurement, and pre-installation testing to ensure that installation verticality, fit clearance, and fixing firmness met construction requirements.

During the tunneling process, a 24-hour real-time monitoring system was implemented on site, with key parameters including shield tail grease injection volume, grease pressure, grouting pressure, tunneling speed, and attitude deviation being closely monitored. According to changes in stratum hardness and groundwater level, operating parameters were adjusted dynamically to identify and address potential issues such as brush wear, steel wire deformation, and local leakage at an early stage. These measures ensured stable operation of the shield tail sealing system throughout the construction period.

During the entire tunneling cycle, the shield machine completed a total of 926 rings of safe excavation, with an average daily advance rate of about 12 rings. The project successfully overcame multiple challenges, including tunneling beneath municipal roads, residential communities, and underground pipeline groups. Throughout the entire process, the shield tail brush sealing system remained stable, with no shield tail leakage, brush damage, or sealing failure occurring. Shield attitude control was precise, segment assembly quality was excellent, and the tunnel alignment fully met the design specifications.

Behind the reliable performance of the shield tail brush system is also the continuous innovation and manufacturing experience of professional suppliers. As a company specializing in shield tail brushes, Chenxing Machinery has accumulated extensive experience in the research, development, and production of shield tail brush products. The company has produced more than 1.2 million sets of shield tail brushes, and its products once achieved approximately 70% market share in China, making it a recognized hidden champion in the domestic shield tail brush industry. Among companies exporting similar products, Chenxing Machinery is one of the few manufacturers that focuses exclusively on shield tail brushes rather than producing a wide range of shield machine accessories.

With years of professional manufacturing experience and large-scale engineering applications, Chenxing Machinery's shield tail brush products have been widely applied in metro projects, highway tunnels, water conservancy projects, and other underground engineering construction. The company continues to optimize product structures, materials, and manufacturing processes to improve sealing performance under high water pressure, long-distance excavation, and complex geological conditions.

The successful breakthrough of the Shanghai Airport Link Line shield section not only represents an important milestone in the city's rail transit development but also provides valuable experience for similar shield tunneling projects in soft soil strata. With the continuous expansion of global tunnel construction, shield machines are being applied in increasingly complex environments, creating higher requirements for key components such as the shield tail brush. Relying on professional manufacturing capabilities and accumulated engineering experience, high-performance shield tail brushes will continue to play an important role in ensuring safer, more efficient, and more reliable shield tunneling operations in the future.