Under sleeper pads provide vibration protection, preserve the ballast under the tracks and improve track stability. They can be installed both in high-speed rail lines and in lines with high axle loads, as well as in existing standard gauge lines, during repairs and retrofitting.
Thanks to an optimised bonding system, GNEE under sleeper pads are pre-fitted to the sleepers during the manufacturing stage. As a result, no additional work is required at the installation site. Installation is quick, unaffected by weather conditions and can be carried out with minimal service interruptions.
What is the function of the under-tie (sleeper) pad?
Under-tie (sleeper) pads are elastic layers placed between railway sleepers and ballast to reduce vibration, noise, and ballast wear, increasing track stability, component life, and ride comfort. They achieve this by increasing the contact area between the sleeper and ballast, which lowers contact pressure, cushions impacts, and distributes loads more effectively, particularly in areas like tunnels, bridges, or high-speed lines.
Key Functions:
- Vibration & Noise Dampening: Absorb shock and reduce transmission of vibrations and noise, improving passenger comfort and protecting surrounding structures.
- Ballast Protection: Prevent ballast breakdown and settlement by cushioning impacts, extending the time between track maintenance (tamping).
- Improved Track Stability: Create a more uniform track stiffness, leading to better track geometry and overall stability, especially where ballast depth is limited.
- Extended Component Life: Reduce stress and abrasion on sleepers, rails, and fasteners, thereby increasing the lifespan of track elements.
- Enhanced Performance: Useful in high-speed, heavy-haul, and urban rail systems to manage increased dynamic forces and demands for reliability.
What are the materials used to manufacture Under Sleeper Pads?
Under Sleeper Pads (USPs) are primarily made from durable, resilient elastomeric materials like rubber (SBR, EPDM), polyurethane (PUR), and EVA (ethylene vinyl acetate), often bonded with resins or containing reinforcing fibers for added strength and vibration damping, with some manufacturers using recycled rubber from end-of-life tires for sustainability.
Key Materials & Types:
- Rubber Compounds: Natural rubber, Styrene-Butadiene Rubber (SBR), and Ethylene Propylene Diene Monomer (EPDM) are common for their excellent vibration isolation and durability.
| Technical Parameter | Unit | Value |
| Stiffness | KN | 90-130 |
| Hardness Shore A | ℃ | 72-80 degree |
| Electronic Resistance | Ω | ≥ 106 |
| Tensile Strength before Aging | Mpa | ≥12.5 |
| Elongation before Aging | % | ≥250 |
- Polyurethane (PUR): Known for its superior elasticity and ability to embed ballast, providing excellent load distribution and vibration damping.
- EVA (Ethylene Vinyl Acetate): Offers good resilience and shock absorption.
| Technical Parameter | Unit | Technical Requirement | Value |
| Density | g/cm3 | 0.95-0.98 | 0.95 |
| Tensile Strength | Mpa | ≥15 | 16 |
| Elongation | % | >500 | 550 |
| Melting Point | ℃ | 170-190 | 170 |
| Insulation Resistance | Ω | ≥1×1010 | 5.0 ×1010 |
| Hardness | A | ≥90 | 92(A) |
- Resin-Bonded Rubbers: High-quality rubber granules (like recycled tires) are bound together with resins to create dense, strong pads.
- Reinforced Materials: Some pads embed fiber materials (like glass or synthetic fibers) within elastomer layers for increased puncture resistance and structural integrity.
As a professional rail fastener manufacturer, GNEE RAIL can produce various types of rubber rail pads with different materials, such as natural rubber, EVA, HDPE and so on. In railway fastening system, rubber rail pads are often installed between the rail tracks and the concrete railway sleepers.