Relationship between anchoring depth of spikes and pull-out resistance
- What is the standard anchoring depth of spikes?
The anchoring depth of ordinary spikes is 120-150mm, and that of screw spikes is 140-160mm. Insufficient depth will reduce pull-out resistance, and excessive depth will waste materials and may affect sleeper strength. Use a depth gauge during construction, with deviation ≤5mm, ensuring it is within the standard range. The depth of turnout spikes needs to be increased by 10mm to cope with larger lateral forces.
- How much does pull-out resistance decrease for every 10mm reduction in depth?
For every 10mm reduction in depth, pull-out resistance decreases by 15%-20%. For example, when the standard depth is 140mm, the pull-out resistance is 80kN; at 130mm, it may drop to 65kN, and at 120mm to 52kN. Too shallow depth makes spikes easy to loosen under train vibration, especially in curves and braking sections. Strictly control depth to avoid insufficiency.
- How to ensure consistent anchoring depth?
Use installation tools with positioning stops. When inserting, the stop contacts the sleeper surface to ensure uniform depth. Before pouring anchoring agent, check the nail hole depth, and deepen to the standard value if insufficient. After laying, sample 10% of spikes, measure depth with special tools, and rework those with deviation over 5mm to ensure overall consistency.
- What problems can insufficient depth cause to spikes?
Insufficient depth will make spikes have low pull-out resistance, easy to tilt under lateral force, and increase gauge deviation. Long-term use will expand nail holes, loosen spikes, or even pull out, affecting track stability. Regular inspection is required. For spikes with insufficient depth, use supplementary anchoring agent or re-anchoring to restore pull-out resistance.
- Is there a difference in spike anchoring depth for different sleeper types?
The anchoring depth of concrete sleeper spikes is 120-150mm, wooden sleeper spikes 100-120mm (too deep may crack due to low wood strength), and composite sleeper spikes 130-160mm (deeper anchoring is needed to ensure strength). Different sleeper types have different depth requirements, which must be implemented according to design documents during construction to avoid improper depth due to confusion.