Cause Analysis and Treatment Measures of Rail Joint Defects

Cause Analysis and Treatment Measures of Rail Joint Defects

1、 Causes of rail joint defects
(1) After medium maintenance of the line, the track bed is unstable and changes rapidly, especially at the rail joints. If the maintenance cannot keep up, the occurrence rate of low joints will greatly increase, resulting in rail head crushing, rolling damage, and other diseases.
(2) Ballast boiling, mud emission, hardening, and joint collapse have resulted in a reduction in the elasticity of the ballast bed, resulting in an increase in the impact force of the train on the joint. Over time, it is easy to generate low buckle joints.
(3) The rail gap is large, the joint bolts are loose, and the joint angle forms when the train passes, increasing the impact force of the train on the joint.
(4) "The rail end fat edges were not removed in a timely manner. After the rail end fat edges were formed, they were rolled by the train wheels to form spalling blocks at the rail ends, which invisibly caused small joints on the surface of the joint rail joints. In fact, there were already oversized rail joints, increasing the impact of the train wheels on the rail joints, causing rail crawling, widening and uneven rail joints, leading to loose rail joint bolts, and loose clamping plates, not only causing comprehensive joint diseases but also seriously endangering driving safety.".
(5) Due to the material reasons of steel rails and cleats and loose parts, diseases such as insufficient ballast shoulder width and curve superelevation of track bed thickness, uneven sleeper spacing, and poor rail joints have been caused. If maintenance is not timely, centrifugal force will be generated when the train enters the curve, forming joint nozzles, damaging the direction of the line, causing the gradual change rate of short distance track spacing to exceed the standard, resulting in track irregularities, Changing the trajectory of the wheels increases the impact and damage of the wheels to the track. (The nozzles often appear on curves, especially small radius curves, and also on straight lines.)
(6) The fat edges and left and right misalignment of the rail action edges cause irregularities in the gauge, changing the running trajectory of the train wheels and thereby damaging the stability of the track, which is one of the main culprits causing water treatment diseases.
(7) The reason for the rail material. Individual rails may be hard bent and have lower joint quenching strength than other standard rails due to various reasons when leaving the factory. When replacing the rails, the vertical wear of the two rails is uneven, or the horizontal pads at the joints are uneven due to improper maintenance, or the uneven tamping and empty lifting of the joints cause misalignment of the rails, resulting in significant impact damage to the joints by the train wheels, resulting in severe empty lifting of the joints, and poor level of the rails.
(8) The material and grading of crushed stone ballast are poor. Under the repeated action of train loads, the ballast bed is damaged, causing the ballast bed to harden, affecting the quality of maintenance operations, and affecting the tamping effect.
(9) The position of the joint sleepers is not correct and square, which cannot evenly transmit the train load to the track bed and subgrade, resulting in uneven stress on the left and right strands of the same joint.
(10) The setting of superelevation on the curve is unreasonable, and the gravity of the train aggravates the impact of the strand joint under the curve, resulting in low buckle of the joint.
2、 The prevention and treatment of rail joint defects should be started from the following aspects:
(1) Strengthen the maintenance and fastening of rail joint parts and fasteners. Including maintaining a reasonable rail gap value at all times; Regularly inspect and retighten high-strength bolts to maintain joint bolt torque above 500N · m; Apply oil to the cleats and joint bolts to mitigate the impact damage of the train; If the creep exceeds the standard, it can be arranged to evenly distribute the rail joints in spring and autumn, and repeat fastening operations for the rail joints and sleeper fasteners after the operation.
(2) Reasonable road lifting and tamping operation. Due to the fact that the stress and vibration acceleration of the track bed at the joint are much higher than those at non joint parts under the repeated impact load of the train, the track bed at the joint should have good tamping quality. When lifting the joint, the rail surface should be leveled and then tamped on eight sides. Do not lift the joint to form a bulge. In particular, for low thread insulation joints, we first need to clean the ballast bed, replace and supplement new ballast, and then replace the joint clamp plate. Replace the insulation joint (especially the two slot insulation in the middle) with new failed insulation material. Tighten the fastener joint bolts, which can eliminate the high and low misalignment of the insulation joint, and then conduct eight sided tamping.
(3) Regulate the track bed at the joint. The stiffening of rail joint track bed not only significantly reduces the bearing capacity, but also greatly improves the line stiffness, reduces the vibration absorption and isolation performance, and intensifies the residual deformation and various diseases of the line. Use skylight repair to clean the bottom and replace the ballast with a new one. Adjust the grading of the ballast at the joint, carefully select the ballast, replace it with small gravel of 20 to 40mm within the range of 5 holes at the joint, and strengthen the tamping on eight sides to evenly distribute the train load transmitted through the rail and sleeper through the roadbed.
(4) Refurbish the rail surface. Uneven wear, chipping, and abrasion at the rail end are significant additional impacts on locomotives and vehicles caused by rail joints during operation, exacerbating line deformation, and leading to the further development of diseases. The joint rail surface must be repaired, polished, and welded in a timely manner. Frequently instruct the road patrolman to observe whether the standard is met every day and replace it in a timely manner.
(5) Improve the elasticity of the cushion under the rail. After years of operation, the elastic cushion under the rail will gradually harden the rubber pad, especially under the strong impact force of the pad at the joint. The elasticity gradually decreases, and the pads of the four sleepers in the joint area should be replaced in a timely manner to restore the good elasticity of the track structure.
(6) Especially for the lines that have just been mechanically cleaned, it is necessary to strengthen joint maintenance: ① Keep the geometric state of the joint track in good condition; ② Timely handle joint hardening, ballast collapse, and mud pouring to improve the elasticity of the track bed; Timely clean and screen the falling ash, coal ash, ash residue during train operation, as well as the invasion of sand, dust, and external loose materials brought in by wind; ③ Timely polish the saddle type and low head buckle, weld and repair the joint rail chippings, and maintain the smoothness of the rail surface; After welding repair, use a 1m long ruler to check that the height of the repaired part does not exceed 0.5mm. After polishing and grinding, the rail surface reaches a flat, smooth, and uniform level.
(7) Treatment of rail misalignment: ① The first method for high and low rail surface misalignment is to use two dental implants on both sides of the rail to pad the splint and the lower jaw of the rail at the low rail end, or to pad dental implants on both sides of the rail at the high side for treatment. The other method is to loosen the joint, knock off the joint clamp plate and pad the horizontal pad, and then tighten the joint bolts and fasteners. If the high and low dislocations are serious, the above methods can be used to eliminate them. ② For left and right dislocations, it can be solved by placing a piece of dislocated teeth, or by placing double layer spring washers and other washers. For the above tightening of joint bolts, it is necessary to tighten the joint while pressing the clamping plate.
(8) Treatment of rail fat edges: Due to the existence of rail gaps at the rail joints, which are also the weak points of the line, the impact of the train wheels at this point is large, which can easily cause crushing at the rail joints, making the rail head larger, making it easy to have a small section of rail fat edges at the action edge, while other parts do not have them, making the gauge percentage seriously uneven and easily affecting the performance of track inspection vehicles and dynamic addition, It is also one of the main factors for artificial feeling of shaking the car, and it should be timely polished with a corner grinder or chopped off with a chop. The fat edges of other parts should also be timely polished with a grinder.
(9) Maintain the correct position of the joint sleepers, and the sleeper spacing must be calculated and set according to the number of configured sleepers. If there is any deviation, use the skylight to repair the square sleeper.
(10) I believe that the treatment of abutment defects can be carried out by using several working methods, such as reversing the splint or replacing two splints, changing lanes, and bending rails. The reason for reversing the clamping plate is that the rail joint is limited by the factory process of the clamping plate and the centrifugal force generated when the train passes on a small radius curve, resulting in poor orientation of the nozzle or joint, which over time forms a hard bend between the rail and the clamping plate. Reversing the clamping plate inside the skylight point can be achieved by hard bending the clamping plate to form a triangular angle, which in turn can be used to just hold the rail joint outward and straight inward (if the nozzle is severe, it can also be padded between the clamping plate and the rail in the middle of the joint by adding a staggered tooth piece on the outside of the nozzle). If it doesn't work, use a large nylon seat to change direction. According to the degree of support nozzle, appropriately increase the width of the outer track bed, and tamp it in layers to increase the resistance of the track bed. Replace the inner and outer mouth splints at the nozzle, and use the reverse bending of the splint to control the joint nozzle. At the same time, during the track shifting operation, the nozzle joint can only be pressed, not picked up. If it is necessary to lift up, use the method of pulling the small waist to drive the joint. Do not directly pull the joint to prevent the nozzle from expanding.
Of course: In order to eliminate rail joint defects, laying seamless rail is the best solution.

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