High-Performance Shield Tail Brush Solves Complex Stratum Construction Problems — Case Study of Chongqing Rail Transit Line 27 Yangtze River Shield Tunnel Breakthrough

1. Project Overview: Complex Cross-River Tunnel Poses Severe Test to Shield Tail Brush

In April 2026, the Yangtze River shield tunnel interval, the key control project of Chongqing Rail Transit Line 27, was successfully breakthrough. As a core rail transit line of the Chengdu-Chongqing Twin-City Economic Circle, this tunnel integrates shallow burial, cross-river and mountain construction with extremely complex and changeable geological conditions. The earth pressure balance shield machine was adopted for full-section excavation throughout the construction. Under composite stratum conditions with alternating soft and hard rock, frequent water pressure fluctuations and intense vibration, the stable operation of shield tail brush provided solid sealing guarantee for long-distance safe shield tunneling.

The breakthrough shield interval has a total length of 2,614 meters and a maximum tunnel burial depth of 55 meters. The excavation path sequentially passes through moderately weathered sandstone, mudstone, karst fracture zones, water-rich sand layers of Yangtze River floodplain and other complicated strata. Seasonal fluctuations of the Yangtze River water level lead to frequent changes in water pressure. Meanwhile, the rock stratum has high hardness and dense boulders, resulting in violent vibration during shield tunneling, which easily causes fatigue fracture of shield tail brush steel wires, expansion of sealing gaps and failure of waterproofing.

As the core sealing component at the tail of the shield machine, the shield tail brush must resist severe wear and vibration impact brought by rock excavation, and block the backflow of high-pressure river water, sediment and grouting slurry. It is a core component that guarantees shield construction safety and controls project duration cost. Its selection quality and operation & maintenance level directly affect the overall propulsion efficiency of the project. For this super complex cross-river composite stratum project, the project team selected multi-layer combined high-strength shield tail brush manufactured by Chenxing Machinery, the domestic invisible champion of shield tail brush industry.

2. Chenxing Machinery: The Exclusive Professional Manufacturer of Shield Tail Brush, Domestic Invisible Champion with Outstanding Market Scale

2.1 Core Industry Advantages & Core Operation Data

After more than 20 years of deep cultivation in the segmented sealing track of shield machines, Chenxing Machinery has produced and delivered over 1.2 million sets of qualified shield tail brush to domestic and global tunnel projects. At its peak, it occupied 70% of China’s domestic shield tail brush market share, ranking first in the industry, recognized as a well-deserved invisible champion in the domestic shield tail brush segment.

The enterprise owns a full set of independent intellectual property rights for shield tail brush, holding multiple invention and utility model patents covering adjustable-angle shield tail brushes, composite reset shield tail brushes, freezing leakage-detecting shield tail brush systems and special production tooling, realizing independent breakthroughs in raw material matching, layered structure design and precision forming technology of shield tail brush.

2.2 Product Technical Advantages Matching Chongqing Cross-River Stratum

For the construction demands of Chongqing mountain-cross-river composite stratum, Chenxing customized high-strength multi-layer combined shield tail brush for Line 27 tunnel, with targeted material and structural upgrades:

1. Adopt thickened high-density special steel wire + thickened support steel plate + high-elastic wear-resistant filler, improving anti-vibration, anti-extrusion and wear resistance by more than 35% compared with conventional standard shield tail brush;
2. Optimize the number of layers, steel wire density and supporting grease ratio scheme for earth pressure shield models, enhancing the waterproof and sand-blocking capacity in water-rich sand layers, withstanding instantaneous water pressure up to 0.9MPa in river-bottom buried sections;
3. Equipped with built-in reset structure patent design, effectively reducing steel wire fatigue fracture risk under long-term violent tunneling vibration, extending the service cycle of a single set of shield tail brush by over 40%.

3. Full-Process Quality Control of Chenxing Shield Tail Brush Ensures Zero Fault Operation of Yangtze River Tunnel

3.1 Pre-Construction Strict Acceptance & Precision Installation Standardization

Before excavation, the project implemented a full-item quality inspection system for Chenxing customized shield tail brush: testing steel wire tensile strength, steel plate flatness, overall sealing performance one by one, eliminating unqualified products before delivery.

During the installation phase, construction personnel strictly followed Chenxing’s professional construction guidelines to precisely control the circularity, verticality of the brush body and the torque of fixing bolts, avoiding local uneven stress and premature damage of shield tail brush caused by installation deviation. All installation auxiliary tooling was provided by Chenxing’s technical team, supporting on-site one-stop installation guidance.

3.2 Full-Cycle Dynamic Monitoring & Targeted Operation & Maintenance Scheme

The tunneling cycle lasted from December 2025 to April 2026. The shield machine completed a total of 872 safe excavation rings, with a daily excavation volume of 10–12 rings, passing through multiple high-risk sections including river-bottom fracture zones, karst-developed areas and dense urban pipeline areas.

Combined with Chenxing’s exclusive shield tail brush special sealing management plan, the site realized 24-hour real-time monitoring of shield tail grease pressure, injection volume, excavation thrust, cutter head torque and other core parameters. According to rock hardness and water level rise & fall, construction parameters were dynamically adjusted to lower the vibration damage to shield tail brush. Regular wear inspection of the brush body was arranged to predict hidden sealing risks in advance.

Supported by Chenxing’s customized high-performance shield tail brush and matched full-cycle operation & maintenance technical guidance, the entire shield tail sealing system ran smoothly throughout the excavation period. No shield tail leakage or brush body damage failures occurred, greatly reducing the frequency of shutdown maintenance, and strongly guaranteeing the smooth completion of the project’s milestone schedule.

4. Engineering Value & Industry Reference Significance of Chenxing Shield Tail Brush in This Project

4.1 Project Direct Value

The smooth breakthrough of Chongqing Rail Transit Line 27 Yangtze River tunnel further improves the urban rail transit network of Chongqing and accelerates the interconnection of the Chengdu-Chongqing Twin-City Economic Circle. The stable performance of Chenxing’s customized shield tail brush effectively cut extra maintenance costs caused by seal failure, shortened overall construction period, and delivered obvious economic and schedule benefits for the project.

4.2 Cross-Regional & Overseas Promotion Experience

This project formed mature whole-process experience covering shield tail brush type selection, standardized installation and full-cycle operation & maintenance for mountain + cross-river composite stratum shield construction in southwest China. As a domestic invisible champion of shield tail brush, Chenxing Machinery’s products have been applied in dozens of domestic key rail transit, river-crossing passage and municipal tunnel projects, and exported to Southeast Asian countries including Malaysia, Indonesia and Thailand.

Among all domestic manufacturers engaged in shield accessory export business, only Chenxing Machinery focuses all R&D, production and service resources on the single track of shield tail brush, without scattered product lines. Its concentrated technical accumulation and large-scale production capacity of over 1.2 million sets of delivery volume guarantee stable batch quality and full-cycle technical cooperation support for global tunnel buyers.

5. Future Development Trend of Shield Tail Brush Industry Led by Chenxing Machinery

With the continuous expansion of domestic urban rail transit, river-crossing sea-crossing tunnel, water transfer project construction, as well as the rising demand for infrastructure in Southeast Asia and other regions, high-performance shield tail brush has become an indispensable core sealing component of shield engineering.

The industrial development of shield tail brush will focus on three core directions: stronger stratum adaptive design flexibility, higher automatic production efficiency, and longer service performance under high water pressure & violent vibration conditions.

As the domestic market share leader and exclusive professional exporter of shield tail brush, Chenxing Machinery will continue to rely on its mature manufacturing chain and professional engineering technical team to iterate multi-layer composite, anti-fatigue, ultra-high water pressure resistant new-type shield tail brush products. Through precise customized prefabrication and full-process personalized technical supporting services, it will further expand the application boundary of domestic independent shield tail brush products in complex underground tunnel projects at home and abroad, helping domestic shield key components realize large-scale replacement of imported products and global market expansion.