Railway Bridge & Tunnel Engineering

Prepared by:Ghanashyam prajapati(13cv88)

Railway Track- Construction, Drainage & Maintenance

Need for Construction of a New Railway LineStrategic reasons

The defense forces can move quickly to the some areas in case of any emergency such as the threat of war.

Political reasons

A new line sometimes becomes necessary to serve the political needs of the country.

Development of backward areas

Railway lines are sometimes constructed to develop backward areas.

To connect new trade centers

Sometimes new trade centers are connected with railway lines for the quick transportation of goods.

To shorten the existing rail link

The existing routes between two important points may be longer than required. New railway lines are constructed on a shorter alignment in such cases

Construction of a New Railway LineThe construction of a new railway track can be divided into

three stages.

1. Earth work.

2. Plate laying

3. Laying of ballast

Earth workThe formation may be in an embankment or a cutting depending upon the general topography of the area.

A formation in an embankment is normally preferred from the point of view of good drainage.

The height of embankment above highest water in the area should be at least 60 cm.

Gauge Type of formation

Width ofSingle line

FormationDouble line

B.G Embankment 6.10m 10.82m

Cutting 5.40m 10.21m

M.G Embankment 4.88m 8.84m

Cutting 4.27m 8.23m

Plate laying The operation of laying out of the rails and sleepers over the ready formation is known as plate laying.

The point from where the laying of track starts is known as the base and the point upon which the new track is carried out is known as the rail head.

Methods of plate laying

1.Tramline method or side method

2.Telescopic method

3.American method

Laying of ballastThe ballast is normally spread on the railway lines after the embankment has settled well and at least two monsoons have passed over it.

The work of spreading the ballast is done by means of ballast trains, which have special hoppers through which the ballast can be automatically unloaded onto the track.

Alternatively, ballast is loaded in wagons of the train and then unloaded at the site into a number of heaps at suitable intervals along the track.

Then packing of ballast is done by the workers by means of shovels.

Track DrainageTrack drainage can be defined as the interception, collection and disposal of water from, upon or under the track. It is accomplished by installing a proper surface drainage and sub-surface drainage system.

Sources of water in a Railway Track.

1.Surface water due to rain, dew, snow.

2.Seepage water from adjacent area.

3.Moisture sucked up by capillary action resulting in increase of moisture in the subgrade or embankment.

4.Hygroscopic water or held water

5.Rain water surface

water)

Source of water in a railway track

Track drainage systemA good track drainage system should essentially ensure that no water percolates into the track at either the surface or the sub-surface levels.

The efficiency of a modern track depends upon the strength and stability of the formation which in turn depends upon the good track drainage.

Track drainage should be handled in two distinctive phases

1.surface drainage

2.sub-surface drainage

surface drainagesurface water due to rain, snow or from adjacent areas should be drained off properly by designing well-planned and effective surface drains.

For bank and formation, good quality soil having well graded particles and high internal friction should be used. The soil should not swell or shrink with variation in moisture content.

The surface water is first collected in well designed side drains and cross-drains which is further disposed off at the nearest stream or natural water course.

Cross drainage structures like culverts and bridges may be necessary for disposing of the surface water.

Sand pilesSand piles Sand drains may be used for the removal of surface water from the embankment. In this method, holes of 30 cm diameter and 1.8 to 3.0 m deep are made between two rails and on the sides of the rails in the embankment. These holes are filled with coarse sand thus forming sand piles.

Functions of sand piles are

1.to support the track.

2.sand piles compact the soil and provide mechanical support to the subgrade just like wooden piles.

3.The drainage of the subgrade also improves, as water rises to the surface through the sand piles by capillary action and evaporates.

Sand piles

Side drainsSide drains should be provided along the track cutting and zero fill locations, where in the cess level is not above the ground level.

Fig. shows the typical cross section of a side drain. Side drain must have an adequate gradient and cross section to enable the free flow of collected water.

All side drains should be provided with concrete lining.

Side drains

Sub-surface drainageThe variations in moisture content of subgrade or embankment are mainly caused due to :

1.Fluctuations in movement of capillary water

2.Seepage water from adjacent area

3.rising of ground water table

4.Percolation of rain water, etc.

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

Drainage of capillary waterThe capillary rise in the embankment can be prevented by the ballast as shown in the embankment or inverted filter of pervious material below the ballast as shown in fig.

Drainage of seepage waterIn case of track in cuttings, the water seeps from adjacent area to sub The surface water entering the subgrade is prevented by providing catch water drains at the cutting and side drains as shown in Fig.

Objectives of maintenance of railway trackThe strength of track structure goes on reducing due to high speed of heavy axle loads and repetition of loads.

The track structure is subjected to other deteriorating effects like rain water, of sun and wind. The wear and tear of rails and rolling stock is bound to take place.

The track structure has to bear so many other curvatures, speed and load particularly on curves, points and crossings.

Advantages of good maintenance

1. The life of both track as well as of rolling stock increases.

2. The journey becomes easy and comfortable.

3. Increase in safety.

4. Saving in operating costs as fuel consumption is less.

5. Safety of passengers and goods encourages more and more use of railway.

6. Higher speed of trains is achieved.

Types of maintenance1. Daily maintenance

2. Periodical maintenance

Daily maintenancemaintenance is carried out by the full time staff maintained throughout the year. The use of maintenance gangs, all along the railway track, is made. The railway track is divided into suitable sections 5 to 6 km length.

1.To check the bolts of fish plates and tighten it if necessary.

2.To check the rail gauge

3.To check the joints

4.To check the fittings of sleepers and rails

Periodical maintenancePeriodic maintenance is carried out after an interval of two to three years .

1.Levelling of rails2.Track alignment3.Gauge4.Proper drainage5.Track components6.Bridge and its approaches7.Rolling stock8.Points and crossings