Causes and Remedial Techniques of Rail Joint Misalignment
What is misalignment at a rail joint, and what are its two main categories?
Misalignment at a rail joint refers to a vertical or horizontal misalignment at the ends of the two rails at the joint. It is divided into vertical misalignment (higher than lower) and horizontal misalignment (left and right). Misalignment disrupts the continuity of the rails, forming impact steps, and is a major cause of joint damage.
What are the main causes of misalignment at rail joints?
Insufficient bolt torque or looseness; poor fit between the fishplate and the rail; wear, crushing, and deformation of the rail ends; uneven track bed settlement; sleepers not properly secured; poor tamping; excessive lateral force on curved sections causing rail misalignment; mixing of old and new rails; inconsistent rail types; and installation positioning errors.
What are the hazards of misalignment at joints to the track and train operation?
Misalignment generates a strong impact, leading to bolt shearing, fishplate breakage, and fatigue cracking of the spring clips; exacerbating rail end crushing, spalling, and core damage; causing sleeper damage and track bed pulverization; causing increased vehicle bumps, vibration, and noise, and in severe cases, requiring speed limits.
What are the criteria and permissible limits for misalignment in rail joints?
According to railway engineering technical standards, the vertical and horizontal misalignment of rail joints on main lines must not exceed 0.5mm; for station tracks and secondary lines, it must not exceed 1mm; and for high-speed and ballastless track sections, it must be controlled within 0.3mm. Any deviations exceeding these limits must be corrected.
What are the main corrective measures for misalignment in rail joints?
Tighten or replace the joint bolts to ensure the torque meets the standard; grind or weld the rail ends to restore smoothness; tampe, patch, and adjust the track bed to eliminate gaps; replace deformed or worn fishplates; and properly configure rail gaps to control rail expansion and creep.