Understanding the different types of movement and deformation in railway tracks is crucial in civil engineering. The question asks about the specific term used for the longitudinal movement of a rail.

Identifying the Longitudinal Movement of Rail

In railway engineering, rails are subjected to various forces and stresses due to moving trains, temperature changes, and ballast condition. These forces can cause the rails to move or deform in different ways.

The term that specifically describes the forward movement of a rail along its length, typically in the direction of traffic, or sometimes against it, is known as creep of rail.

Detailed Analysis of Options

Let's examine the provided options to understand why 'Creep of rail' is the correct term for longitudinal movement and why the other options are incorrect in this context.

1. Wear of rail: This refers to the loss of rail material from the surface due to friction and abrasion caused by the wheels of passing trains. Wear is a reduction in cross-section or profile, not a longitudinal movement of the entire rail.
2. Hogging rail: Hogging is a form of vertical deformation where the rail bends upwards between supports (sleepers), typically near joints or due to uneven support. It is a vertical curvature, not a longitudinal displacement.
3. Crushed rail: This term usually describes a localized defect where the rail head material is deformed or fractured, often due to excessive impact or overloading. It signifies material failure or damage, not a general longitudinal movement of the rail length.
4. Creep of rail: This is the phenomenon where the rail slowly moves longitudinally in the track. Creep is a significant maintenance issue as it can lead to various problems like buckling, distortion of points and crossings, and sleeper skewing if not controlled.

Based on these definitions, the longitudinal movement of a rail is precisely defined as Creep of rail.

Understanding Creep of Rail

Creep of rail is caused by several factors, including:

• Forces exerted by train wheels (traction, braking, impact).
• Expansion and contraction due to temperature variations.
• Ballast condition (loose or unstable ballast allows movement).
• Gradient of the track.
• Poorly maintained joints.

Controlling creep is important for track stability and safety.

Comparing Rail Movements and Defects

To further clarify, here is a simple comparison:

Therefore, the longitudinal movement of a rail is correctly termed 'Creep of rail'.

Revision Table: Railway Track Terminology

Additional Information on Rail Creep

Controlling rail creep is a vital aspect of railway track maintenance. Various methods are employed to mitigate creep:

• Anchorage: Using rail anchors or anti-creep devices that grip the rail foot and bear against the sleepers, transferring the longitudinal force to the ballast.
• Proper Fastenings: Using elastic fastenings that provide sufficient grip on the rail and prevent it from moving longitudinally relative to the sleepers.
• Welded Rails: Continuous Welded Rail (CWR) significantly reduces the number of joints, which are common points for creep initiation. However, CWR introduces thermal stresses that need careful management.
• Adequate Ballast Resistance: Ensuring the ballast is clean, well-compacted, and provides sufficient resistance to the movement of sleepers.

Effective control of creep ensures track stability, prolongs the life of track components, and maintains safety for train operations.