Track Drainage CE2303 Railway Engineering

Drainage-General Drainage is the natural or artificial removal of surface and sub-surface water from an area.

General-Track Drainage Track-drainage involves the interception and removal of water from, upon or under the track is done by surface drainage system as well as sub-surface drainage system.

Sources of Moisture 1.Surface water (rain water) 2.Moisture due to capillary action 3.Seepage water from adjacent area 4.Hydroscopic water / held-water

Rain Water

Capillary Water

Seepage Water

Hydroscopic Water

Sources of Water in Railway Track

Sub-surface Drainage The excess of moisture due to capillary action or water seeped from adjacent area is removed and diverted by lowering the water table (by some method) and as termed as sub-surface-drainage.

Water Table

Significance of Track-drainage

Settlement of Track If excess moisture available in the soil will result in reduction of bearing capacity of soil. This result in settlement of railway track in the soil due to heavy wheel load. Hence the excess moisture needs to be removed.

Requirements of Track-drainage

Water Content There should not be any excess water on or below track section on all seasons.

Drainage System 1-Surface Drainage

Source Rain water is the major source of surface water in India.

Movement of Surface Water Surface water pass into soil by the action of gravity. The movement depends on permeability of soil.

Collection of Surface Water First collected in well designed side drains and cross-drains – disposed off to the nearest stream or water body.

Side Drains

Cross Drainage of Water

Turfing of Side Slopes Economic method to prevent the entry of water is to provide turfing on the side slopes of embankment or cutting and on the cess (portion of formation beyond the space occupied by the ballast)

Turfing

Sand Piles Surface water from the embankment can also be drained by use of sand piles.

Sand Piling

Sand Piles In this method, a series of holes of 30 cm dia. are driven with a steel instrument inside as well as outside of rail up to a depth of 1.8 m to 3.0 m and then filled with sharp clean sand and the track is resurfaced.

Plan Showing Sand Piles

Sand Piles These holes are driven vertically into subgrade or formation (specially through water on weak pockets) by means of augers or similar tools or by driving wooden piles and then taking them out.

Functions of Sand Piles Function as timber piles Provide good mechanical support Provide vertical drainage by capillary rise of moisture to the surface and surface evaporation

Drainage System 2-Sub-surface Drainage

Sub-surface Drainage Changes in moisture content of sub-grade or formation in embankment or in cutting are caused mainly due to fluctuations in movement of capillary water, seepage water from adjacent area, ground water table and percolation of rain water.

Objective The object of sub-surface drainage is to keep these fluctuations of moisture as minimum as possible.

Sub-surface Systems

Drainage of capillary water Drainage of seepage water

Drainage of Capillary Water The best method of preventing the capillary rise is to provide pervious layer in the embankment as shown in figure.

Drainage of Seepage Water In case of track in cutting, the water seeps from adjacent area to sub-grade as shown in figure.

Drainage of Seepage Water A water bearing strata impounds its water because it has no escape. Impound: Shut-up in an enclosure

Drainage of Seepage Water In such cases, the construction engineer should determine the source which feeds this water bearing strata and should divert it to the surface of interception.

Drainage of Seepage Water This water is further collected and carried away to some point of outfall where it can have no further adverse effect on the track.

Drainage of Seepage Water The surface water entering the sub-grade is prevented by providing catch water drains as shown.

Drainage of Seepage Water Further to check seepage through catch water drains, the drains should be paved.

Drainage of Seepage Water The water from catch water drain is finally disposed off in natural river or water course.

Drainage of Seepage Water In case of formation in cutting, the side drains are also provided with perforated pipes (or blind-pipes) underneath to lower the ground water table as shown.