ballastless tracks

7/24/2019 Ballastless Tracks

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A Seminar On

Ballastless Tracks

BY

MANU SHIVANAND B050394CE

TOM JACOB B050397CE


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Need

Development Design

Prevalent ballastless systems

Requirements Characteristics

Problems


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Introduction

Ballast has been an integral part of railway track for manyyears.

It is an economical medium providing an elastic support to thesleepers and absorbs major part of the noise created by passingwheels.

Material is locally available. But ballasted track calls forfrequent maintenance attention, and periodical screening.

It causes dust pollution. Hence, railways all over have beenresearching and developing a more permanent track base, inform of ballastless track for their high speed lines.

In ballastless tracks the ballast is substituted by support layerof concrete slabs

Though they will be more expensive, they will be most cost

effective for such lines.


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Need For Ballastless Tracks

The three basic requisites of laying a good railway track are economy, safetyand comfort.

Traditional tracks on wooden and metal sleepers with good ballast cushionsatisfied all these requirements in the normal traffic conditions.

Increased traffic density and increased speeds on railways became necessary tosuit growing economy and competition.

In such cases the conventional tracks were found lacking.

These require better load distribution requiring increased ballast cushion;stabler track with minimum joints leading to development of CWR andconcrete sleepers

More time is required for track maintenance operations due to increasedfrequency of trains.

Ballasted tracks are also becoming more difficult to maintain due to theirgetting pounded under heavier loads causing drainage problems.

They also cause rise of dust by the trains passing at higher speeds, adverselyaffecting the environment.


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Development of ballastless tracks

The Japanese tried some form of BLT (ballastless track) in one of their subways in

1947.

It appears Teito Rapid Transit Authority is perhaps the first railway to useballastless track on a larger scale.

In about same period, London Transport used in their underground sections a

design by embedding wooden sleepers at ends in a concrete bed, leaving the space

between filled with ballast. At the same time different forms of such tracks were being tried by a number of

other railway systems for their subways both on the main lines in tunnels and Metro

lines.

Switzerland and Germany were the forerunners in use of BLT on main line andMoscow for their (Metros) subways on a large scale.


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Ballastless Track Used In Tozai Line


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BALLASTLESS TRACK DESIGN AND

DEVELOPMENT The various types of BLT initially were{during the 70s}

Laying concrete sleepers or blocks over a base or deck slab and subsequently

stabilizing by pouring grout or concrete around them (Budapest and Sonneville). Laying tracks complete with fasteners and dowels on auxiliary sleepers supported

by special props and subsequently pouring longitudinal beams below (Cologne,

Germany).

Laying a continuous RCC floor on tunnel floor or over formation, laying rails withrubber pads and elastic fastenings in position and fixing to concrete slab with

proper holding down/anchoring (Japan and UK).

Laying the concrete slab to proper tolerances and then fixing the rail with base

plates and rubber pads on the same with proper holding down arrangements(Netherlands).


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Prevalent Ballastless Systems

1.Fixed Base Continuous RCC Plinth

Hong Kong Metro

Continuous Slab UK and Europe; Kolkata Metro

2.Floating Slab With Continuous Resilient Medium

Japan-Shinkansen lines; Germany-Berlin Metro Resilient Pads at Intervals

Atlanta Metro; Honk Kong Airport line

3.Sleepers/Sleeper Blocks Inset in Concrete

Timber Provided at turnouts and locations where lateral shifts are expected

Twin Block Sleepers with Boot . ( Sonneville, Stedef etc)

Channel Tunnel; Europe, Hong Kong Metro


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Basic Requirements Of Ballastless Tracks

Stability;

Durability; Elasticity;

Suitable fastening system:

Minimum maintenance; Ease of replacement of sleeper/fastening:

Economy


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Main Characteristics Of A BLT

low maintenance

high availability increased service life

low structure height

low weight high lateral track resistance which allows future speed

increases in combination with tilting technology

no problems with churning of ballast particles at high-speed


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Problems Of BLT

Materials type concrete being more expensive in supplyingand building than ballast,these type of tracks are less

economical

They are structures without systematic geometric corrections

during the cycle of life

It does not allow important settlement for the soil support.

BLT is generally noisier than ballasted track Increased ground vibrations


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Conclusion

In order to satisfy various conditions mentioned, the specific attributes ofgood ballastless track for choice in Indian conditions should be with

Proven design . having been in service for a number of years. Economy in cost of construction.

Durability . long life for components, specially rubber and cushioningmaterial which will require replacement during life time of the base andsuitability for Indian weather and maintenance conditions.

Minimum number of patented components. Easy and economical maintainability . ease of change of parts with

minimum dislocation to traffic.

Ease in restoration of traffic in case of accidents/derailments.

Effective drainage of track. Noise pollution and vibration control within practicable limits.


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References

Ballastless Track for Urban Transit Lines,Dr S Ponnuswamy,

Ballastless tracks, Dr Hans Bachmann UIC Infrastructure Commission Civil Engineering Support

Group


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Thank You

ballastless tracks

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