Choosing Spike Length and Tie-Down Strength
- In wooden sleeper tracks, how to choose the length of spikes?
Wooden sleepers are relatively soft, and the length of spikes needs to ensure sufficient anchoring depth while avoiding piercing the wooden sleepers. Generally speaking, when the thickness of wooden sleepers is 160 - 220mm, the length of spikes is 120 - 160mm, and the length anchored in the wooden sleeper is not less than 80mm, which can provide sufficient gripping force to prevent the spikes from loosening. If the spike is too short, the anchoring depth is insufficient, and it is easy to be pulled out under train vibration; if it is too long, it may pierce the wooden sleeper, affecting the strength and service life of the wooden sleeper.
- In concrete sleepers, what is the relationship between the length of spikes and the fixing strength?
Concrete sleepers have high strength and hardness, and the length of spikes needs to be determined according to the depth of pre-embedded sleeves in the sleepers or the anchoring method. When using sulfur anchoring, the length of the spike should make the anchored part go deep into the concrete sleeper by not less than 100mm to ensure the anchoring force; when using bolt spikes, the length of the threaded part entering the sleeper must meet the design requirements (generally 60 - 80mm) to ensure sufficient connection strength. Insufficient length of the spike will lead to insufficient fixing strength, and excessive length may exceed the thickness of the sleeper, affecting installation and use.
- How does the thickness of different sleepers affect the selection of spike length?
When the sleeper thickness is large (such as concrete sleepers with a thickness of more than 200mm), longer spikes need to be selected to ensure sufficient anchoring depth, and the length of the spike is usually 180 - 220mm. When the sleeper thickness is small (such as some light wooden sleepers with a thickness of 140 - 160mm), the length of the spike should be shortened accordingly, generally 100 - 140mm, to avoid damage to the sleeper caused by excessively long spikes. When selecting, it is necessary to match the anchoring length of the spike with the thickness of the sleeper according to the actual thickness of the sleeper to ensure the fixing effect.
- How to detect whether the length of the spike meets the requirements of fixing strength?
Carry out a pull-out test, install the spike on the sleeper according to the specified length, use a pull-out instrument to apply tension, and measure the maximum pull-out force when the spike is pulled out. If the pull-out force reaches the design standard (generally not less than 60kN), it indicates that the length of the spike meets the requirements. In the actual track, observe whether the spike is loose or displaced. If there is no obvious loosening of the spike after the train has been running for a period of time, it also indicates that the length of the spike is appropriately selected and the fixing strength is up to standard.
- What problems will be caused by improper selection of spike length?
If the spike is too short, the anchoring depth is insufficient and the fixing strength is insufficient. Under the action of train load and vibration, the spike is easy to loosen and pull out, resulting in the failure of the connection between the rail and the sleeper, changes in the gauge, and affecting driving safety. If the spike is too long, it may pierce the wooden sleeper and cause it to crack; for concrete sleepers, it may exceed the range of the sleeper, interfere with other components, or cause uneven stress on the anchoring agent, reduce the anchoring effect, and increase maintenance costs.