Anchoring and Pull-out Performance Requirements for Rail Spikes
Why does the pull-out resistance of rail spikes need to be ≥100kN?
Rail spikes need to bear the longitudinal and transverse loads transmitted by rails. Insufficient pull-out resistance will cause the spikes to loosen and fall out, resulting in failure of the connection between sleepers and ballast. The pull-out resistance of ≥100kN can ensure that the spikes remain stable under high-frequency vibration and load impact of trains and prevent track displacement. Sufficient pull-out resistance can resist the track expansion stress caused by temperature changes and avoid gaps between the spikes and the anchoring agent. In heavy-haul lines, the huge train load will generate greater pull-out force on the spikes, and the high-standard pull-out resistance is the guarantee for safe operation. In addition, meeting the pull-out resistance standard can extend the service life of the spikes, reduce the frequency of maintenance and replacement, and lower operating costs.
What are the key steps of the anchoring process for spiral rail spikes?
First, it is necessary to clean the anchoring holes in the sleepers to remove impurities and accumulated water, ensuring the anchoring agent is closely combined with the hole wall. Mix the anchoring agent in proportion, stir evenly and quickly inject it into the hole to avoid bubbles and delamination. Insert the spiral rail spike into the anchoring hole slowly, ensuring the position is centered and vertical to avoid inclination affecting the stress. Wait for the anchoring agent to cure. The curing time must meet the product requirements, generally not less than the specified hours, and the spike is not allowed to be disturbed during this period. After curing, check the installation quality of the spike to ensure no loosening or skewing. Subsequent track laying can be carried out only after the pull-out resistance meets the standard.
What are the common anti-corrosion treatment methods for rail spikes?
Common anti-corrosion treatment methods for rail spikes include hot-dip galvanizing, film coating anti-corrosion and coating treatment, among which hot-dip galvanizing is the most widely used. Hot-dip galvanizing can form a uniform zinc layer on the surface of the spike, isolating air and moisture, effectively preventing rust and adapting to the outdoor humid environment. Film coating anti-corrosion covers a special film on the surface of the spike, which has both anti-corrosion and lubrication effects, facilitating installation and having strong durability. Coating treatment uses anti-corrosion coatings, such as epoxy resin coatings, which can specifically resist specific corrosive environments, such as salt spray corrosion in coastal areas. Different anti-corrosion methods should be selected according to the line environment to ensure that the spikes do not suffer severe corrosion during the service period.
What is the significance of the cold bending performance test for spiral rail spikes?
The cold bending performance test can verify the toughness of the spike material and avoid the spike breaking during installation or use due to excessive brittleness. During the test, the spike is bent 15° according to the specified indenter diameter (72mm), and no cracks are considered qualified, ensuring the spike can withstand external forces during installation. Good cold bending performance means that the spike can absorb energy through slight deformation when subjected to train load impact and line deformation without brittle fracture. Spikes with unqualified cold bending performance are prone to cracks under complex stress conditions, affecting the overall connection reliability. In addition, this test can screen out products with uneven materials or internal defects to ensure the quality of the spikes.
What factors need to be considered when selecting the anchoring agent for rail spikes?
The strength of the anchoring agent is the core. Products with high compressive strength and bond strength should be selected to ensure a firm combination with the spikes and sleepers. The setting time needs to be adapted to the construction requirements, not only ensuring sufficient operation time during construction but also rapid curing to improve construction efficiency. The anchoring agent must have good aging resistance, no cracking or falling off during long-term use, and maintain the anchoring effect. It should adapt to changes in ambient temperature and maintain stable performance under extreme high and low temperature conditions without affecting the pull-out resistance. In addition, the environmental protection of the anchoring agent should be considered to avoid environmental pollution, while taking into account the convenience of construction.