Anchoring Methods and Pullout Resistance of Rail Spikes
- What are the anchoring methods of spikes? Which scenarios are they suitable for?
Spike anchoring mainly includes three methods: sulfur anchoring, resin anchoring and mechanical anchoring. Sulfur anchoring is suitable for temporary or low-speed lines with wooden and concrete sleepers, with low cost but easy embrittlement at low temperatures; resin anchoring is suitable for high-speed railways and electrified railways, with fast curing, high strength, environmental protection, and can adapt to various climate conditions; mechanical anchoring is fixed by expansion bolts or clips, suitable for temporary tracks that need frequent disassembly or sleeper test sections, with flexible installation but slightly poor long-term stability.
- How does the proportion of resin anchoring agent affect the pull-out resistance of spikes?
The proportion of resin, curing agent and filler in resin anchoring agent is crucial. Excessive resin content will reduce strength, and insufficient resin will result in poor fluidity; the deviation of curing agent proportion exceeding ±5% will lead to too long or too short curing time, affecting the anchoring effect; uneven particle size of filler (such as quartz sand) will reduce the compactness of the anchoring agent. With a reasonable proportion, the pull-out resistance of resin-anchored spikes can reach 80-100kN, and the pull-out resistance may decrease by more than 30% when the deviation is too large.
- What factors are related to the pull-out performance of spikes?
The strength of the spike's own material affects the pull-out performance, and spikes made of high-strength steel have higher pull-out resistance; the bonding strength between the anchoring agent and the sleeper and spike, rough-surfaced spikes and clean nail holes can enhance the bonding; the embedding depth of the spike, generally ≥100mm in the sleeper, too shallow will significantly reduce the pull-out resistance; the sleeper material, the anchoring force of concrete sleepers is usually higher than that of wooden sleepers because they combine more closely with the anchoring agent.
- How to test the pull-out performance of spikes?
Use a special pull-out testing machine to connect the tension sensor with the spike, apply tension at a uniform speed of 5-10kN/min, and record the maximum tension value at the moment the spike is pulled out; randomly sample 3-5 spikes from each batch for testing, and take the average value as the pull-out resistance of the batch; after testing, check the damage form of the spike and anchoring agent. If the anchoring agent is separated from the sleeper, it indicates that the anchoring process has problems and needs to be re-optimized.
- What problems should be paid attention to in spike anchoring in cold regions?
Sulfur anchoring should be avoided in cold regions because it is easy to be brittle below -20℃. Cold-resistant resin anchoring agents (minimum service temperature -40℃) can be used; before anchoring, ice, snow and frozen blocks in the nail holes must be removed, and the sleeper must be preheated to above 5℃ if necessary; spikes should be made of galvanized or stainless steel to prevent low-temperature rust; after anchoring, heat preservation measures must be taken to ensure that the anchoring agent cures within the specified time, avoiding prolonged curing time due to low temperature affecting strength.