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Metro bolts (also known as tunnel segment bolts or shield segment bolts) are essential fasteners used in segment tunnel construction, and are designed in both straight and curved shapes to connect the precast concrete segments that form the circular tunnel lining.
Types of Metro Bolts
Types of Metro Bolts
There are two types of metro bolts: longitudinal straight bolts and circumferential arc bolts. In some projects, the specifications of 2 types of bolts are the same, while in others, they have different specifications and strength grades. Metro bolts also have another name. They are called segment tunnel bolts.
Function of Metro Bolts
Function of Metro Bolts
The primary function of these bolts is to link several arched segments together to form a stable, cylindrical pipe that supports the entire tunnel surface during and after excavation. This support system effectively controls ground settlement and reduces impact on surface structures.
Design of Metro Bolts
Design of Metro Bolts
Tunnel segment bolts are classified by their shape and head type. The main types include:
Straight Segment Bolts: Used for longitudinal connections (along the length of the tunnel) or in specific projects where the geometry allows.
Curved (Arc-shaped) Segment Bolts: Engineered with a specific radius of curvature to fit the contours of the arched segments, used for circumferential connections (around the tunnel ring). The arc shape ensures proper alignment and even stress distribution across the connection point.
Other classifications based on head type include:
Double-ended straight/curved segment bolts
Hexagonal curved segment bolts
Hexagonal head circular curved threaded segment bolts
Hexagonal flange curved thread segment bolts
Materials and Treatment
Materials and Treatment
Given the underground, humid environment of tunnels, which makes bolts prone to corrosion, specific materials and surface treatments are crucial for durability.
Materials: High-quality carbon steel and alloy steel, with common strength grades including 5.8, 6.8, and 8.8 (using materials like Q235, 45# steel, or 40Cr).
Surface Treatment: Common anti-corrosion measures include hot-dip galvanizing (HDG), dacromet coating, and sherardizing, which provide long-term rust resistance (e.g., a galvanized layer of 85-100μm can last over 50 years).
Kunshan Signum Machinery Technology Co.,Ltd is capable of using specialized processes, involving molds, to ensure the precise arc of curved bolts so they fit correctly during installation and maintain the tunnel's structural integrity.
Manufacturer and Supplier Of Metro Bolt
Manufacturer and Supplier Of Metro Bolt
Kunshan Signum Machinery Technology Co.,Ltd is able to supply straight or curved metro bolt for tunnel construction according to customers' requirements or drawing with competitive price.
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Email: admin@rail-fastening.com
Web: www.rail-fastening.com
Address: 120 Tongjing Road, Lujia Town, Kunshan, Jiangsu 215331, China
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