Formation

The surface prepared to receive the ballast, sleepers, rails, etc.. for constructing the railway track is called Formation or sub grade.

Function of formation

• The formation has the following functions
• It provides a smooth and uniform bed on which the track is laid.
• It bears the entire load transmitted from the moving loads to it through the ballast.
• It provides drainage facilities.
• It provides stability to the track.

DESIGN ASPECTS

Width

• The width of the formation depends upon
• Numbers of tracks to be laid over it.
• Gauge of the track.
• Width of ballast layer.
• Width of drains provided.

 

Height

• The height of the formation depends upon the topography of the alignment and the gradients adopted.

Slide Slopes

• The slide slopes of the formation depends upon the characteristics of the soil, as shear strength, angle of repose etc.