Subject : Mumbai University > Civil Engineering > Sem 6 > Transport engineering 2

Creep:

The creep of rails is the longitudinal movement of rails in a track. It is also called as travel of rails.

Theories of creeps:-

1. Wave action or wave theory:-

   As train is passing under the rolling wheel, the portion under rolling wheel is compressed and depressed slightly due to wheel loads. As wheel moves, this depression also moves and the portion which is under depression previously comes back to its original position. This produces wave action which causes creep in forward direction.

2. Percussion theory:-

   This type of rail creep occurs mainly due to impact of wheel. In this type, when wheel pass over joint, the trailing rail depresses down and wheel gives impact to the end of facing rail which results in creep.

3. Accelerating or starting of a train:-

   At time of acceleration, wheel gives backward thrust which causes creep.

4. De-accelerating or stopping of train, due to application of breaks:-

   If sudden stopping takes place, breaking effect tends to push the rail forward and thus causes creep in forward direction.

5. Alignment of track:-

   Creep is more on curved portion than straight portion.

6. Expansion and contraction of rails is happens due to temperature variation. Creep may also cause due to expansion and contraction of rails.