Performance and Anchorage Quality of Rail Spikes
- What are the main performance indicators of spikes?
They include tensile strength. Spikes need to have sufficient tensile strength to resist pulling force. The tensile strength of ordinary spikes is ≥375MPa, and that of screw spikes is ≥400MPa. Hardness is also an important indicator. The hardness of the spike head should be moderate, which is easy to install and not easy to deform, generally between HB180 - 230. Corrosion resistance: in humid, dusty and other environments, spikes need to have good corrosion resistance. The zinc layer thickness of galvanized spikes is ≥8μm. In addition, the straightness deviation of the spike must not be greater than 1mm/m to ensure smooth installation.
- What are the differences between spikes adapted to different types of sleepers?
Ordinary spikes are usually used for wooden sleeper tracks. Their shanks are thick, which can be better embedded in wood to provide sufficient grip. They can be fixed by tapping during installation, and the cost is low. Concrete sleepers need to use screw spikes. Because of their hard texture, ordinary spikes are difficult to fix. Screw spikes can generate large pulling resistance by combining with the anchoring agent in the sleeper through threads. Steel sleeper tracks generally use welded spikes, which are directly welded to the steel sleepers to ensure high strength and stability of the connection, adapting to the rigid characteristics of steel sleepers.
- What are the common methods of spike anchoring? What are their characteristics?
The sulfur anchoring method is a traditional method. Sulfur, cement, sand, etc. are mixed in proportion, heated and melted, then injected into the nail hole, and the spike is inserted to solidify. It has high anchoring strength, but attention should be paid to safety during construction to avoid sulfur gas hazards, and it is easy to embrittle in low - temperature environments. The resin anchoring method uses materials such as epoxy resin, which has the advantages of fast curing, high strength and environmental protection. It is convenient to construct, not affected by low temperature, and suitable for electrified railways and seamless lines, but the cost is relatively high. The mechanical anchoring method connects the spike with the sleeper through mechanical devices, which is flexible to install and easy to disassemble and replace, suitable for temporary tracks or sections that need frequent adjustment.
- How to ensure the firmness of spike anchoring?
Before anchoring, it is necessary to clean up the debris and water in the nail hole to ensure that the anchoring agent can fully contact the hole wall and enhance the bonding force. Select anchoring materials that meet the requirements. For example, the proportion of sulfur anchoring agent must be strictly controlled, and resin anchoring agent must be used within the shelf life. The spike must be inserted vertically to avoid uneven stress caused by skew, and the insertion depth must meet the regulations. Generally, the height of the top of the spike exposed on the sleeper surface is consistent. After anchoring, sufficient curing time is required. Sulfur anchoring needs to be cooled to normal temperature, and resin anchoring needs to wait for curing according to the instructions to avoid premature stress affecting the anchoring effect.
- What are the testing methods for spike anchoring quality?
Pull - out test is the main method. A special tensiometer is used to conduct pull - out test on the spike. The pull - out force of ordinary spikes should be ≥60kN, and that of screw spikes should be ≥80kN. If it is lower than the standard, re - anchoring is required. Appearance inspection: check whether the spike is vertical, whether the anchoring agent is full, and whether there are cracks, empty drums, etc. If so, repair or rework is required. Tap inspection: tap the spike with a small hammer. A clear sound indicates that the anchoring is firm, and a dull sound may indicate empty drums, which need further inspection and treatment.