Creep Of Rails

What Is Creep Of Rails 

The Rails have the tendency to move gradually in the direction of dominant traffic . Hence Creep Of Rails is defined as the longitudinal movement of rails with respect to sleepers in a track . Creep may varies in magnitude like at some places it can be negligible and somewhere it can be in few centimeters , but it is common to all rails .  

What Are Indications Of Creep 

Creep of Rails can be noticed in the following way :-

1. Marks on flanges and webs of rails made by spike heads , by scraping or scratching on the rails         slide . 

2. Closing of  successive expansion spaces at rail joints in the direction of creep and opening out of joints at the point from where the creep starts .

Theories Of Creep 

Following are some described theories of creep of rails :-

1. Wave Action or Wave Theory of Creep 

It explains the loads of wheel on rails as the reason for creep of rail . As the wheel move , the lift in front of the moving load is thus carried forward by the wheels and causes creep .

The pitch and depth of wave depends upon following :-

a. Track modulus                                                     b. Stiffness of track

c. Stability of formation .

2. Percussion Theory of Creep

Percussion theory states that creep of rails occurs due to impact of wheels at the joint ends , since effect of single wheel is negligible but due to the comulative effect of wheels results in sufficient creep in rails . 

  According to this theory following are the certain points due to which creep increases

a. when heavy axle load moves on rails 

b. when there is a wide expansion in gap .

c. when fish plates are week .

3. Dragging Theory of Creep 

This theory is similar to wave theory of creep . It states that drving wheel push the rails in backward direction and other wheels pushes the rails in driving direction , this whole process results in introducing creep in rails . 

WHAT ARE THE EFFECTS OF CREEP IN RAILS 

1. Creep in rails produce direct impact on sleepers provided for the rails which results in sleeper's            movement and the movement disturbed the surface and results in uncomfortable riding . 

2. Stresses developed in fish plates and bolts which sometimes result in break .

3. If any rail is removed from the track then it becomes very difficult to put it on the same position         due to creep as in by the time gap it becomes too long or too short . 

4. The rails are also battered at ends due to excessive gaps at joints .