What is rail creep

rail creep

Rail creep is also known as line crawl. The creeping phenomenon of the rail along the longitudinal direction of the line. With the increase in railway transportation tasks, the impact of the wheels on the rails when the train is running accelerates the creep of the rails. Rail creep can cause many diseases of the line. In order to prevent the occurrence of track creep diseases, it is necessary to find out the real cause of creeping in order to effectively eliminate the problem.

There are two different manifestations: the rails move along the soft sleeper surface due to insufficient fastening pressure of the fasteners; the longitudinal movement of the row is caused by insufficient ballast bed resistance. The reason for this is the longitudinal force of the rail caused by the wheel rolling and longitudinal slip, train braking, the change of rail temperature, and the creep caused by the deflection and deformation of the rail under the action of the wheel load. Make the line appear continuous blind seam or large rail seam, pull the inclined sleeper to form joint disease and track gauge, poor direction, etc., until the track loses stability and expands the track. It is possible to install enough line anti-creeping equipment, and then use anti-creeping type rail fasteners and practical and effective ballast bed ramming measures to carry out comprehensive prevention and control.

When the train is running, the wheels act on the rail track, which not only generates vertical force and lateral force but also causes the rail to bend in wave shape under the action of dynamic load due to the rolling and longitudinal sliding of the wheel. Generates a longitudinal horizontal thrust. This longitudinal horizontal thrust can cause longitudinal displacement of the rail, and sometimes also drive the sleepers to move together. This movement is called rail creep.

In short, there are many reasons for creeping, mainly including deflection of rail under dynamic load; longitudinal force of train operation; temperature change of rail; wheel hitting the rail at joint; train braking, etc. When the anti-creeping equipment on the line is insufficient, the buckle pressure of the fastener and the longitudinal force resistance of the ballast bed is not enough, which will aggravate the line crawling. It is generally believed that rail deflection is the main reason for line crawling, while other factors contribute to and exacerbate line crawling.

The measures to prevent line crawling are mainly to increase the longitudinal resistance of the line.

(1) Strengthen the anti-climbing resistance between the sleeper and the rail track bed

The method is to maintain the standard section of the track bed so that the thickness of the ballast under the sleeper is sufficient, the ballast in the sleeper box is full, and the slag shoulders at both ends of the sleeper are wide enough to strengthen the tamping; It is very important to do solid work. According to the measurement, the resistance of each wooden sleeper in the direction of the line is about 500kg for the uncompacted gravel bed. The rammed one is about 800-1000kg. In addition, the seriously dirty track bed must be cleaned to prevent the longitudinal resistance of the line from being reduced due to the mud and the line climbing to the bottom.

(2) Strengthen the function of anti-climbing equipment and anti-climbing equipment

It is to prevent the track from creeping, improve the longitudinal movement resistance of the track, and strengthen the buckle pressure of the intermediate fastener and the clamping force of the joint splint. Anti-climbing equipment includes anti-climbing devices and anti-climbing supports. Anti-climbing devices include spring anti-climbing devices and pin-type anti-climbing devices. Pin-type anti-climbing devices are widely used in my country’s railways. Each of these anti-climbing devices can withstand a crawling force of 3000kg and is composed of rail clips with baffles and pins. One side of the rail card tightly clamps the rail bottom, and the gap between the other side and the rail bottom is wedged with a wedge-shaped pin to make it firmly stuck on the rail bottom. In order to make full use of the anti-climbing ability of the pin-type anti-climbing device, it is also necessary to connect a pair of anti-climbing devices and 3 to 4 sleepers with anti-climbing supports to form a set of anti-climbing equipment to jointly resist the transmission of the anti-climbing device. track crawl force. The anti-climbing support can be made of wood, stone, and reinforced concrete. Install the anti-climbing device and anti-climbing support according to the requirements of the specification, and add anti-climbing equipment if necessary. The failed anti-climbing equipment should be replaced and repaired in time.

(3) Maintain the proper buckle pressure of the fastener

In order to increase the resistance between the rail and the plywood, between the rail and the backing plate, and between the backing plate and the sleeper, the bolts should be tightened in time, and the floating spikes and the fasteners should be tightened. The failed road studs and fasteners should be replaced and repaired in time.

(4) Remediate joint diseases in time

Diseased joints will aggravate the impact of the train on the rails and increase the crawling of the rails. Therefore, the saddle-type wear joints, low joints, and damaged rail heads should be refurbished in time. For continuous large rail joints and sections with uneven rail joints, adjustments should be made.

Line crawling is the root of all diseases, it will cause the sleeper position to be skewed, the spacing is not correct and the rail seam is uneven. When the rail crawls, it often drives a part of the sleeper and the joint sleeper to move together. In this case, the splint will drive the road studs to crack the sleeper or make the sleeper leave the original tamped and solid bed surface, resulting in various diseases on the rail joints, which must be rectified in time.

When the train is running, it will have a longitudinal force (mainly friction) with the rail, which will cause the rail to move longitudinally, and sometimes even drive the rail to move together. This phenomenon is called track crawling.

Rail creep often causes line diseases such as uneven track seams and skewed sleepers, which are extremely destructive to the track and even endanger driving safety in severe cases. Therefore, measures must be taken. The main measure is to install anti-climbing facilities on the track. Commonly used Anti-climbing facilities are pin anti-climbing devices and anti-climbing braces.

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