Anti-pull-out structural design of rail spikes and long-term reliability assurance of track bed anchorage
What are the core design forms of the anti-pulling structure of railway spikes?
The core design forms of the anti-pulling structure of railway spikes include barb-type structure and thread segment composite structure, and the two forms can be used alone or in combination. The barb-type structure is to set 3-5 circles of annular barbs on the spike shank. The inclination angle of the barbs is 30°-45°, the height is 3-5mm, and the width is 5-8mm. The direction of the barbs is opposite to the spike insertion direction, which can effectively resist the upward pulling force and prevent the spike from loosening and pulling out. The thread segment composite structure is to set a coarse thread segment with a length of 50-80mm at the lower part of the spike. The thread profile is triangular with a tooth height of 4-6mm. The bonding area between the thread segment and the concrete ballast bed is 40%-50% larger than that of the smooth shank spike, improving the anchoring force. The combined structure is to set both barbs and thread segments on the spike shank, with the barbs above the thread segment. The two work synergistically, and the pulling resistance is 30%-40% higher than that of the single structure, suitable for heavy-haul and high-speed lines.
What are the anchoring performance differences between anti-pulling structure spikes and ordinary spikes?
The anchoring performance differences between anti-pulling structure spikes and ordinary spikes are mainly reflected in three aspects: pulling resistance, anti-loosening ability and durability. The pulling resistance of anti-pulling structure spikes can reach 80-100kN, which is 2-3 times that of ordinary spikes, and can effectively resist the pulling force generated by the lateral load of trains; the pulling resistance of ordinary spikes is only 30-40kN, which is prone to pull-out failure in heavy-haul lines. The anti-loosening ability of anti-pulling structure spikes is strong, and the anchoring force loss rate is ≤5% under 1×10⁶ vibration loads; the anchoring force loss rate of ordinary spikes can reach 20%-30%, requiring frequent retightening. In terms of durability, the service life of anti-pulling structure spikes can reach more than 15 years, while that of ordinary spikes is only 5-8 years, requiring regular replacement. In addition, the anti-pulling structure spikes have better adaptability to the ballast bed concrete, and will not cause concrete cracking due to excessive anchoring force.
What are the adaptation requirements of anti-pulling structure spikes for different ballast bed types?
The adaptation requirements of anti-pulling structure spikes for different ballast bed types are core to matching the stiffness of the ballast bed and the characteristics of the anchoring medium. The integral concrete ballast bed has high stiffness and high concrete strength (above C50), and is adapted to combined anti-pulling structure spikes with 5 circles of barbs, a thread segment length of 80mm, and a pulling resistance ≥100kN to meet the anchoring requirements of high-speed lines. The anchoring medium of the slab ballast bed is resin mortar with high bonding strength, and is adapted to thread segment composite structure spikes with a thread segment length of 60mm and a tooth height of 5mm. No barbs are needed to avoid damaging the track slab structure. The sleepers of the crushed stone ballast bed are concrete sleepers with limited anchoring depth, and are adapted to barb-type structure spikes with 3 circles of barbs and a barb height of 3mm to ensure that the sleepers are not damaged when the spikes are inserted. The stiffness of the transition section ballast bed changes greatly, and is adapted to adjustable anti-pulling structure spikes, which can adjust the effective height of the barbs according to the ballast bed stiffness to maintain stable anchoring force.
What are the key processing technology points of anti-pulling structure spikes?
The key processing technology points of anti-pulling structure spikes are concentrated in two links: forming accuracy of barbs and threads and heat treatment to ensure stable structural performance. The barb forming adopts cold extrusion process, and the precision of the extrusion die must reach ±0.05mm to ensure that the deviation of the barb angle, height and width is ≤±0.1mm, avoiding barb deformation affecting the anchoring effect. The thread segment processing adopts thread rolling process, and the thread rolling pressure is controlled at 80-100MPa to ensure full thread profile without defects, and the thread precision reaches grade 6g. The heat treatment adopts integral quenching and tempering treatment, the quenching temperature is 830-860℃, and the tempering temperature is 400-430℃, so that the hardness of the spike shank reaches HRC35-40, and the hardness of the barb and thread parts reaches HRC45-50, balancing strength and toughness. After processing, a pulling test should be carried out, and the pulling resistance of the sampled spikes must reach more than 100% of the design value.
What are the key on-site anchoring construction points of anti-pulling structure spikes?
The key on-site anchoring construction points of anti-pulling structure spikes need to focus on anchoring hole forming and spike insertion process to ensure anchoring reliability. The anchoring hole forming adopts a special drilling machine, the drilling diameter is 2-3mm larger than the diameter of the spike shank, and the drilling depth is 10-15mm deeper than the designed anchoring depth of the spike to ensure sufficient anchoring space after the spike is inserted. After drilling, it is necessary to clean the concrete debris and dust in the hole with a high-pressure air gun, then inject anchoring agent, the filling amount of the anchoring agent is 80%-90% of the hole volume, avoiding difficult spike insertion due to excessive filling. The spike must be inserted vertically, and the insertion speed is controlled at 50-100mm/min to ensure that the barbs and thread segments are fully combined with the anchoring agent. After insertion, static curing is required for ≥24 hours, and the load can be applied after the anchoring agent is completely cured. After construction, pull-out sampling inspection should be carried out with a sampling ratio of 5% per batch, and the pulling resistance must meet the design requirements.