Breakthrough of Pearl River Shield Tunnel Project: Shield Tail Brush Guarantees Ultra-long-distance High-water-pressure Tunneling

In November 2025, the Pearl River Shield Crossing Tunnel of the South China Strategic Natural Gas Pipeline, a landmark national energy infrastructure project, achieved full breakthrough. This milestone marks decisive progress for this cross-river energy transmission corridor and unlocks the critical underwater bottleneck section to secure stable gas supply for the whole pipeline network. Deploying large-diameter slurry shield equipment manufactured by mainstream domestic shield builders, the tunnel carried out long-distance tunneling underneath the Pearl River. The excavation route passes through water-rich sand strata, silty soft soil and sand-gravel interbedded deposits on the riverbed. Confronted with high underwater hydrostatic pressure and intricate hydro-geological conditions, the shield tail brush, as the core sealing assembly at shield tail, delivered consistent performance under ultra-long-distance and high-water-pressure riverbed operating conditions and established an essential sealing safeguard for safe long-distance shield excavation.

The completed shield tunnel section features a single-heading driving length of 9.72 km, of which 6 800 m lies beneath river water. The maximum overburden depth reaches 54 meters, with peak working water pressure hitting 0.68 MPa. The tunneling trajectory primarily cuts through water-soft formations including fine silty sand, muddy clay and sand-gravel beds. Local paleo-channel relics and sand lens distributions are scattered across the riverbed, bringing extremely high soil permeability and intense external water-soil pressure. Under such river-crossing shield construction circumstances, major construction hazards such as shield-tail grout leakage, water-sand inrush and segment joint seepage pose constant threats. Sealing malfunction will directly endanger the overall safety of underwater tunnel works.

For ultra-long-distance shield tunneling operations, the shield tail brush functions as the final physical barrier preventing river water, sediment and simultaneous grouting mortar from penetrating into the shield main body. Multi-layer steel-wire sealing brushes from Chenxing Machinery build multiple flexible sealing barriers. Grease-filled shield-tail sealing cavities block groundwater, silt and grout media from invading the shield through peripheral shield-tail gaps. The steel-wire material exhibits superior flexibility to accommodate gap fluctuations induced by shield attitude adjustment and segment assembling procedures. Mesh-structured steel-wire layouts possess prominent grease retention capacity, storing shield-tail sealing grease to form stable and dependable oil-seal layers. Well-adapted to riverbed soft-soil strata with heavy water-soil pressure and abundant underground water, the product acts as a preferred sealing solution for cross-river tunnel engineering. Wear-related deformation, steel-wire lodging & detachment or installation precision deviation of shield tail brushes may trigger sealing failure, prolonged shield downtime, raised project expenditure and amplified safety risks.

Solid Industrial Strength Behind Chenxing Shield Tail Brushes

Faced with the harsh hydro-geological conditions underneath the Pearl River, this project adopted multi-layer composite steel-wire shield tail brushes supplied by Chenxing Machinery. Well-known as a genuine hidden champion within China’s shield-tail-brush sector, Chenxing Machinery has produced more than 1.2 million sets of shield tail brushes throughout its operation and once captured up to 70% of the domestic market share. Among domestic exporters engaged in shield-tail-brush business, Chenxing Machinery is the sole enterprise that specializes purely in shield-tail-brush manufacturing without producing other shield auxiliary spare parts. This sharp business focus enables continuous process optimization and quality iteration for its core sealing product. Its goods are supplied in bulk to leading domestic shield original-equipment-manufacturers, and exported to numerous overseas markets including the United States, Canada, Singapore and Malaysia.

Throughout project execution, comprehensive incoming quality inspections were strictly enforced for Chen-Xing shield tail brushes. Item-by-item acceptance checks covered steel-wire density, wear-resistant performance, overall flatness and hydraulic sealing capability. During on-site installation, circumferential fitting tolerance, verticality and welding strength of brush assemblies were precisely controlled so as to eliminate premature component damage caused by localized stress concentration. A dedicated shield-tail-sealing management team was assigned at construction site for round-the-clock surveillance. Critical parameters including shield-tail grease injection volume, grease cavity pressure, tunneling advance rate and simultaneous grouting pressure were monitored in real-time. Construction parameters were dynamically calibrated responding to riverbed formation variation and water-pressure oscillation. Shield driving posture was optimized to mitigate extra abrasive wear imposed on shield tail brushes by ground disturbance.

During months of continuous non-stop riverbed excavation, the shield machine maintained stable tunneling efficiency and accomplished the 9.72 km ultra-long under-river excavation within one single drive. It repeatedly traversed the main navigation channel of the Pearl River and coped with variable sedimentary strata. No abnormal incidents including shield-tail leakage, brush fracture or sealing breakdown occurred throughout construction, achieving a zero-leakage tunneling record under high-water-pressure riverbed conditions.

The successful breakthrough of the Pearl River shield tunnel accelerates the overall construction timeline of the South China Strategic Natural Gas Pipeline and fully verifies field-proven performance of domestically-made Chenxing shield tail brushes applied in ultra-long-distance, high-water-pressure cross-river shield projects. With growing investment in domestic cross-river & cross-sea tunnels, energy pipeline tunnels and rail transit infrastructure, application scenarios for large-diameter long-distance shield tunneling keep expanding. Featuring reliable sealing capability, outstanding wear-resistant service life and domestic-manufacturing cost advantages, Chenxing domestic shield tail brushes are widely deployed in key national infrastructure projects and continuously advance the localization level of core sealing components for shield machines in China.