Correct Answer - Option 4 : The gauge length remains the same
Concept:
Creep: Longitudinal movement of the rail in tracks in the direction of locomotives.
Major causes for creep in rail are as follows:
a) Forces developed when the train is starting or stopping by application of brakes.
While starting, the wheels push the rail backwards and hence the direction of creep is in the backward direction.
When brakes are applied then the wheels of the vehicles push the rails in the forward direction and hence the creep is in the forward direction.
b) Due to wave motions developed when the wheels of the vehicle hit the crest.
c) Unequal expansion/contraction due to the different temperature gradient along the track.
d) The ballast is forced out of place.
Minor causes for creep in rail are as follows:
a) Rails not properly fixed to sleepers
b) Bad drainage of ballast
c) Bad quality of sleepers used
d) Improper consolidation of formation bed
e) Gauge fixed too tight or too slack
f) Rails fixed too tight to carry the traffic
g) Incorrect adjustment of superelevation on outer rails at curves
h) Incorrect allowance for rails expansion
i) Rail joints maintained in bad condition
