Tunnel environments are uniquely harsh, characterized by constant moisture, piston-effect air pressure from passing vehicles, and the necessity for high fire resistance.
Key Technical Requirements
- Fire Performance & Passive Protection
In a tunnel, a fire can reach extreme temperatures very quickly (the RWS curve or HCinc curve). Tunnel boards must be Class A1 Non-combustible.
- Thermal Insulation: The board must protect the structural concrete or steel lining from "spalling" (where moisture in concrete expands and causes the surface to explode).
- Toxic Fumes: They must be zero-smoke and zero-halogen to ensure visibility and breathability for evacuees.
- Durability & Hydrophobic Properties
Unlike standard siding, tunnel boards are often exposed to groundwater seepage and high-pressure washing.
- Water Absorption: High-quality tunnel boards are autoclaved and often treated with a factory-applied hydrophobic coating.
- Freeze-Thaw Resistance: In colder climates, the board must withstand hundreds of cycles without delaminating or cracking.
- Pressure & Vibration Resistance
The "piston effect" caused by high-speed trains or heavy trucks creates significant positive and negative air pressure.
- Mechanical Strength: The boards are typically thicker (often 12mm to 20mm) and denser than residential siding.
- Fixing Systems: They are usually installed on high-grade stainless steel (316L) sub-frames to prevent galvanic corrosion.
- Common Comparison: Fiber Cement vs. MgO for Tunnels
| Feature | Fiber Cement (Autoclaved) | Magnesium Oxide (MgO) |
| Moisture Resistance | Excellent; very stable. | Risk of "crying" or chloride leaching if not high-sulfate. |
| Impact Resistance | High; brittle but dense. | Very high; excellent flexural strength. |
| Installation | Heavy; requires pre-drilling. | Easier to cut, but requires specific fasteners. |
| Cost | Generally more cost-effective. | Higher-end, specialized high-sulfate boards are pricier. |
More information, please visit at www.hocre-board.com or send message by whatsapp +86 15001321220
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