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Date: 2015-10-07; view: 517.

Use the scheme to give the definition of “Railway Track”.

Substructure

UNIT 3

I.

II.

Subgrade is the finished surface upon which the Track is built. It is designed to:

- have sufficient strength to support the loads passed down from the rails through the sleepers and ballast;

- provide water drainage.

Before the beginning of subgrade earthworks the engineers carry out preliminary study of the area, then they perform site clearing, removal of topsoil and unsuitable material, excavation, cutting of terraces into slopes, scarifying and compaction of embankment base, provision of drainage works, sampling and testing.

Subgrade design includes: embankment (1), cutting (2), sidehill fill (3), sidehill cut (4), cut and hill (5)

(1) (2)

(3) (4) (5)

Embankment is a stabilized fill formation above the natural ground to a determined cross section and longitudinal profile to accommodate the railway and any associated infrastructure.

Cutting is an excavation of the natural ground to a determined cross section and longitudinal profile to accommodate the railway and any associated infrastructure.

Water is never desirable in earthworks. The service life of subgrade depends to a high degree on the quality of the drainage facilities.They include:

- top and side drains along the railway reserve to direct water away from the rail track formation to recognized water courses;

- pipes installed expressly to collect water from between or beside tracks and direct it away to a recognized side drain or watercourse;

- waterways constructed under the track, whether pipes, culverts, or similar.

To provide subgrade stability and protection from natural effects (flood water, stone downfalls, snow slips, drifting snow, avalanches, stone downfalls, sand drift, wet landslides, earthquakes, etc.) consolidated structures are made: prestressed concrete slabs (1), counter pilasters (2), ripraps (3), breakwave walls (4).

(1) (2) (3)

(4)

Engineering Structures (ES)– complex of structures used for Permanent Way at the intersection with various obstacles. ES are of two main types: bridge structures (bridges, culverts, trestles, viaducts, overpasses) and tunnel structures (tunnels, galleries, retaining walls, balconies).