Railway Ballast Properties

Flashcards for reviewing railway ballast properties lecture.

Railway Ballast

A crushed granular material that supports the rails and sleepers in a rail track.

Functions of Ballast

Provides a level bed, holds sleepers, transfers load, provides elasticity, resistance, drainage and maintains track alignment.

Properties of Good Ballast Material

Hardness, Angularity, Size (20-50mm), Cleanliness, and Durability.

Granite

A highly durable ballast material commonly used in heavy-duty tracks providing excellent drainage and stability.

Basalt

A hard and dense ballast material suitable for high-traffic lines, resistant to wear and tear.

Limestone

A cost-effective ballast material, less durable than granite or basalt.

Gravel

A ballast material used in secondary or low-traffic lines, requiring more maintenance.

Slag

An economical ballast material, a byproduct of steel production, providing good drainage but may not be as durable as natural stone.

Sandstone

A soft and less durable ballast material, not ideal for high-traffic areas.

Load Distribution (Ballast Function)

Spreads the load from the sleepers to the subgrade, preventing track deformation.

Track Alignment (Ballast Function)

Maintains the correct alignment and level of the track.

Drainage (Ballast Function)

Prevents water accumulation, which can weaken the track structure.

Elasticity (Ballast Function)

Provides flexibility to absorb dynamic loads from trains.

Noise Reduction (Ballast Function)

Dampens noise and vibrations from passing trains.

Permanent Deformation

Settlement of the track bed due to frictional slip between ballast particles.

Ballast Degradation

Breakdown and contamination of ballast, leading to poor drainage, instability, and settlement.

Mud Pumping

Occurs when water mixes with fine particles from the subgrade creating a slurry.

Contamination Causes

Dirt deposition, Tamping damage, Subgrade mixing and High contact stresses.

Ballast Fouling

When the ballast layer changes its composition and becomes finer in grain size distribution.

Resilience

The ability of a material to return to its original shape or position after an applied load has been removed.