Download - 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