This Article Covers About Track Drainage In Railway Like Need, Requirements And Track Drainage System One By One.
Track Drainage In Railway
Track drainage can defined as the interception, collection, and disposal of water from, upon, or under the track. It accomplished by installing a proper surface and sub-surface drainage system.
Need for Proper Track Drainage
Water is the greatest threat to a railway track, and the most prominent factor that adversely affects track maintenance is improper drainage.
Excess water affects the stability of the embankment, and the bearing capacity of the soil and its resilience to shear gets considerably reduced.
Railway engineers give maximum importance to the proper drainage of the track and the need to do so is felt because of the following concerns
Settlement of embankment
- Excess water may cause the embankment to settle.
- An unequal settlement may lead to variation in cross levels as well as longitudinal levels thereby affecting the safety and riding quality of the track.
Reduction in bearing capacity
- The bearing capacity of the soil as well as its resistance to shear diminishes due to excess water in the soil.
- This in turn leads to numerous problems and finally affects the safety and stability of the track.
Failure of embankment
- The percolation of water in the embankment increases the weight of the soil on the one hand and reduces its bearing capacity and shear resistance on the other.
- This makes the formation unstable.
- This is a common reason for the failure of embankments, which occurs in the form of slips.
Formation of ballast pockets
- Excess moisture leads to punctures in the formation.
- The constant hammering action of running trains causes the sleepers to move up and down, resulting in ballast pockets, pumping sleepers, and other such problems.
- All these factors lead to poor riding quality.
Shrinkage and cracking of banks
- The embankment soil cracks and shrinks once excess water dries up.
- The problem becomes acute in the case of poor soils.
- This in turn leads to many problems such as the loss of ballast in the cracks and uneven settlement, which have an adverse effect on track maintenance.
Adverse effects of black cotton soil
- There are certain soils, such as black cotton soil, which become plastic in nature due to the accumulation of excess water.
- The formation shrinks due to change in moisture content.
- The bearing capacity of the soil greatly reduced due to the excess water.
- These problems imperil the safety of the track.
Formation of slush
- Slush formed due to the dynamic load of running trains.
- It forced out, thus badly clogging the ballast.
- This makes the maintenance of the track very difficult.
Sources of Percolated Water in the Track
Water can percolate to the formation of the track through any of the following methods.
This includes water that collects due to rains, etc., moving into the subgrade because of the effect of gravity. This movement resisted by the permeability of the soil.
The effective ways of reducing the progress of water by this method are the following.
- Provision for drainage on the top of the embankment in the form of cross fall, side drains, lowering of cess, etc.
- Turfing of side slopes of the embankment
By capillary action
At times water rises into the subgrade by way of capillary action. The capillary rise of water can prevented by providing a pervious layer in the embankment which serves a capillary break.
From adjacent areas
In this case, water from some nearby source seeps into the subgrade. Water seepage can reduced by taking the following steps.
- Diverting the original source of water
- Providing effective paved catch water drains
- Providing inverted filters and underground drains
By hydroscopic action from atmosphere The moisture present in the atmosphere is comparatively very small and has very little effect on the total moisture content of the soil.
Requirements of a Good Track Drainage Railway System
A good drainage system should satisfy the following requirements.
Surface water should not percolate to track
One of the basic requirements of a good track drainage system is that surface water from rains and adjacent areas should not percolate and seep into the formation of the track.
Effective side drains
The size of the side drains should be adequate with a proper slope, so that they effectively carry all the surface water away.
Longitudinal drains to saucer-shaped
The longitudinal drains provided between two tracks should preferably have a saucer-shaped cross section so that they can collect water from both sides.
Provision for clearing and inspection
The drains provided for drainage should be such that they can inspected and cleared periodically.
Drain top to be below cess level
Normally, the drain top should not be above the cess level for the effective drainage of the ballast bed.
No erosion of banks
The flow of water along the slope and across the track should not cause erosion of the banks or the slopes of the banks.
Formation to be of good soil
Ideally, the formation and subgrade should made of a pervious, coarse-textured soil. Such soils are more permeable, retain less capillary water, and respond more favourably to a surface drainage system.
Proper sub-surface drainage
Arrangements should made for a good sub-surface drainage system to drain off the water retained the track. This is more relevant in the case of defective formations.
Longitudinal drains should designed so as to provide a proper outfall, from where the water can eventually drain off.
Special arrangements for waterlogged areas and other difficult situations
A good track drainage system should have special arrangements for the drainage of waterlogged areas and for all other related perennial problems.
Practical Tips for Good Surface Drainage
The following measures will ensure that the track drainage system gives a good performance.
Maintain proper cess level
Tracks on embankments get drained as long as the proper cess levels maintained and the ballast is clean.
However, in cuttings and in yards, where water cannot recede freely and quickly from the track, a well planned drainage system must be provided.
There should be no growth of vegetation in the track, as this indicates clogging of the ballast and a lack of adequate track drainage.
Such stretches of tracks should overhauled or deep screened.
The ballast should be clean so that rainwater can easily flow out of the track.
Area below rail foot to be clear
About 25 to 50 mm of the area below the rail foot should kept clear of any ballast, earth, or cinder on all lines inside and outside the yards.
This would enable good surface flow as well as avoid corrosion and failure of track circuits.
Cleaning and repair of drains
All drains should cleaned and repaired as a part of annual through packing, not only on run-through lines but also on all other running lines in yards.
Track Drainage Railway Systems
As mentioned earlier, a good track drainage system should essentially ensure that no water percolates into the track at either the surface or the sub-surface levels,
And the arrangements for the drainage of sub-surface water should be good and effective wherever required.
Track drainage should handled in two distinctive phases.
Surface water due to rain or snow, or from adjacent areas should drained off properly by designing well-planned and effective surface drains.
In case water percolates into the formation due to bad soil or such other reasons, the formation gets adversely affected and this has a bearing on the safety and stability of the track.
Surface drainage is dealt with in three different stages covering the entire length of the track.
- Drainage in mid-sections between railway stations
- Drainage in station yards
- And Drainage of station platforms
Drainage in Mid-sections Between Railway Stations
A drainage system between two railway stations consists of the following features.
Side drains should be provided along the track in cuttings and zero fill locations, where the cess level is not above the ground level. The typical cross section of a side drain is shown below.
All drains must have an adequate gradient to enable the free flow of the collected water.
Lining of drains
Side drain lining is imperative on Group A routes and preferable on other routes, except those routes where the drains are in rocky strata.
Adequate opening under level crossing
In order for all the water to flow out of the side drains in cuttings, adequate openings should be provided under level crossings, around trolley refuges, and around the overhead electric masts.
Catch water drain
Catch water drains should be provided wherever necessary, in cuttings. Their size should be worked out according to the volume of the water the drain is expected to carry.
No surplus ballast
Surplus ballast in the shoulders of the track retards drainage and encourages vegetation growth. All extra ballast should be taken out of the track and stacked in small heaps beside the track.
Drainage in Station Yards
When planning the drainage of station yards, the following guidelines should be kept in mind.
Open surface drains
Surface drains should generally be left open to make cleaning and inspection convenient.
When designing in-yard drains, a velocity range of 0.5 to 1.0 m/s may be allotted for earthen drains and 1.0 to 2.0 m/s for lined (or masonry).
As mentioned earlier, the longitudinal drains that lie between two tracks should be saucer-shaped with curved sides.
However, drains with vertical sides may be provided wherever saucer-shaped drains are not practicable.
Drain top not to be above cess level
Normally, the drain top should not be above the cess level for the effective drainage of the ballast bed.
However, if it is essential that a drain with a higher top level be provided in order to retain the ballast, weep holes must also be provided at the assumed cess level and the drain so designed that the water it carrier does not flow the base level of the weep holes.
Outflow and slope
Wherever there is a proper outfall available at either end of a yard, the longitudinal drains provided should have their slopes facing in the direction opposite to the middle of the yard.
This will ensure the minimum size and depth of the drains.
Position of ballast sections
The ballast section in station yards should be the same as that on the main line.
Network of cross and longitudinal drains
Every station yard should have a network of cross and longitudinal drains, whether earthen or masonry, which allows water collected due to storms to be carried away in the least possible time.
The arrangements for surface drainage at water columns and carriage watering points with washing hydrants should be efficiently maintained.
At these locations, Water must be adequately trapped and borne away in a pipe or a lined drain.
Open drain section
Figure shows a detailed sketch of the open drains that are provided between two tracks on a railway line.
Drainage of Station Platforms
The following points should taken into account when planning the drainage system of a platform.
Slopes away from track
Normally, all end platforms should sloped away from the track. The details of the drainage system of a platform illustrated in Fig.
Discharge on non-track side
All drains from platform shelters, tea stalls, toilets, water taps, etc., should be enclosed in pipes and should normally discharge or release their contents on the non-track side of the platform.
Covered longitudinal drains should be provided on the platform, if necessary.
Discharge not towards run-through lines
In the case of island platforms, all drains should discharge their contents on the less important side of the track and not towards run-through lines.
Water normally reaches the sub-surface due to capillary action, seepage from adjacent areas, or percolation of rainwater. When water reaches the sub-surface, it immediately affects the stability of the formation.
The situation becomes worse particularly if the soil is bad.
A variety of problems arise due to the proximity of the water to the subgrade.
The various sub-drainage systems used,
- Provision of inverted filter
- Paving of catch water drains
- Provision of sand piling
- Drainage of water pockets by perforated pipe
- Cement grouting
- Drainage of water pockets by puncturing holes
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