Railway track:An Introduction
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This document discusses various aspects of traditional ballasted railway track, including: - The important functions of ballast in distributing load and providing stability, drainage, and track maintenance. - The standard ballast profile and advantages/disadvantages of traditional ballasted track compared to ballastless track. - Key components of permanent way including rails, sleepers, fishplates, and various types of fastenings. Elastic fastenings help absorb vibrations. - Rubber pads between rails and sleepers are important for damping vibrations and preventing gaps in the track. Proper toe load from fastenings also provides stability and resistance to movement.
Railway track:An Introduction
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- 5. Important Functions of Ballast To transfer and distribute the load form sleepers to a larger area of formation. To provide elasticity and resilience to track for getting proper riding comfort . To provide necessary resistance to track for longitudinal lateral stability . To provide effective drainage to track. To provide effective means of maintaining evenness and alignment of track
- 7. Advantage of Traditional Ballasted Track Advantage • • • • Relatively low construction costs. High elasticity. High maintainability at relatively low costs. High noise absorption.
- 8. Disadvantage of Traditional Ballasted Track Disadvantage • Over time, track tends to ‘float’, in both longitudinal and lateral direction, as a result of non linear, irreversible behaviour of the materials. • Limited non-compensated lateral acceleration in curves, due to limited lateral resistance offered by the ballast. • Ballast can be churned up at high speeds, causing serious damage to the rails and wheels. • Reduced permeability due to contamination, grinding down of ballast and transfer of fine particles from sub grade.
- 9. • Ballast is relatively heavy, leading to an increase in costs of building bridges and viaducts, if they are to carry continuous ballasted track. • ballasted track is relatively high, this direct consequences on tunnel diameter and access points.
- 10. Advantage of Ballastless Track • Reduced Height • Lower maintenance requirement and hence, higher availability for train operation • Increased service life • Lack of suitable ballasted material • A requirement for track to cause(even) less noise and vibration nuisance
- 11. • Ballastless tracks are the good options for high speed heavy haul trains; but on the other hands they are costly also.
- 13. rails Sleepers Ballast Embankment Function •Support & guide vehicles running on it 13
- 14. •Conventional Track •Consists of two “Rails” located at a fixed distance apart •Called “Gauge” •The Gauge of a track is the distance between inner edges of the heads of rails in track, measured at 16mm below the top surface of the rail. 14
- 15. Rails Rails are members of the track laid in two parallel lines to provide on our continuous and land surface for the movement of Trains. Function of rails (a) (b) (c) (d) (e) Provide a continuous and level surface Provide a pathway which is smooth and less friction Lateral guide for the wheels Bear changes due to vertical loads etc. Transfers to formation through sleepers on wider area. 15
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- 17. Coning of wheels – The distance between the inside edges of wheel flanges is generally kept less than the gauge. Gap is about 38 mm on Either side. Normally the tyre is absolutely ahead centre on the head of the rail, as the wheel is coned to keep it in this central position automatically. These wheel are coned at a slope Theory of coning:- On a level track, as soon as the axle moves towards one rail, the diameter of the wheel tread over the rail increases, while It decreases over the other rail. This prevents to further movement And axle retreats back to its original position ( with equal dia or both rails and equal pressure on both rails). 17
- 18. • Advantages of coning of the wheels are :1. To reduce the wheel and tear of wheel flange and rails which due • To rubbing action of flanges with inside to cess of the rail head. 2. To provide a possibility of lateral movement.
- 19. Sleepers Sleepers are transverse ties that are laid to support the rails. They Have an important role in the track as they transmit the wheel load From the rails to the ballast. Functions and requirement of sleepers (a) Holding the rails to their correct gauge alignment (b) Giving a firm and ever support to the rails (c) Transfering the load evenly from rails to a wider area of the ballast. (d) Providing longitudinal and lateral stability the permanent way. Sleeper density and spacing of sleepers Sleeper density is the number of sleeper per rail length. It is M +X Specified on where M– length of the rail 19
- 20. Sleeper Density • M+4 low density traffic < 10 GMT & D & E routes • M+7 – M is the rail length for 13 m rail length M+7 =20 • For Long Welded Track 1540 sleepers per Km or 1660 sleepers per Km 20
- 21. Concrete Sleeper Pre-Stressed Concrete Sleeper (PSC) 21
- 22. REQUIREMENT OF SLEEPER • IT SHOULD PROVIDE EASY MEANS OF MAINTAINABILITY • HANDLING OF RAILS, SLEEPER & FASTENING SHOULD BE EASY • QUICK RESTORATION AFTER ACCIDENT IS POSSIBLE • MATERIAL AND DESIGN IS AVAILABLE • IT SHOULD HAVE ANTI THEFT AND ANTI-SABOTAGE QUALITY • IT SHOULD BE OVERALL CHEAP
- 23. LOAD DISTRIBUTION FROM AXLE TO SLEEPERS
- 24. DESIGN CONSIDERATIONS • THE REACTION AT THE RAIL SEAT DEPENDS UPON------– SLEEPERS SPACING – AXLE LOADS – SPEED OF TRAINS – THE STANDARD OF MAINTENANCE OF TRACK
- 25. DESIGN CONSIDERATIONS • TO CALCULATE THE FORCES TO WHICH THE CONCRETE SLEEPERS ARE SUBJECTED IS COMPLICATED AND IS GENERALLY BASED ON OBSERVATIONS, EXPERIENCE AND MEASUREMENTS.
- 26. DESIGN CONSIDERATIONS • FOR BG (22T AXLE LOAD), A WHEEL LOAD OF 11 T AT THE RAIL TOP WILL CAUSE A VERTICAL SLEEPER REACTION OF 6 T. • FOR MG (14T AXLE LOAD), THIS VALUE IS 5 T. THESE LOADS ARE AUGMENTED BY 150% TO CATER FOR DYNAMIC AUGMENT FOR DESIGN PURPOSE.
- 27. CONDITION NO. 1 NO CENTRE BINDING 15 TONNE 15 TONNE 1750 MM p 670MM 1040 MM 1040 MM
- 28. CONDITION NO. 2 WITH CENTRE BINDING 15 TONNE 15 TONNE 1750 MM p’ p’ 670MM 1040 MM 1040 MM
- 29. CONDITION NO. 3 : Lateral load 13 TONNE 7 TONNE 1750 MM p
- 30. DESIGN CONSIDERATIONS 1.237 CONDITION 2 B.M. CONDITION 3 CONDITION 1 1.277
- 31. DESIGN CONSIDERATIONS • MAX. B.M. AT RAIL SEAT IS GOVERNED BY CONDITION NO.1 • MAX. B.M. AT CENTRE IS GOVERNED BY CONDITION NO.2 • CONDITION NO.3 DOES NOT GOVERN THE MAX. B.M. AT ANY LOCATION AND HENCE IS NOT CONSIDERED
- 32. SHAPE OF SLEEPER IN PLAN – – SHOULD NOT ALLOW CONCENTRATION OF THE BALLAST REACTION IN MIDDLE HENCE TRAPEZOIDAL SHAPE ADDITIONAL LATERAL RESISTANCE DUE TO WEDGING ACTION
- 33. SHAPE OF SLEEPER IN PLAN •SLEEPER PROFILE IS TRAPEZOIDAL BECAUSE IT IS HAVING MORE SECTION MODULUS COMPARED TO RECTANGULAR SECTIONS WITH SAME CROSS SECTIONAL AREA. IT ALSO FECILITATE EASY DEMOULDING AND MORE ROOM FOR HTS WIRES AT THE BOTTOM.
- 34. ADVANTAGES OF PSC SLEEPERS • HEAVY WEIGHT--PROVIDES LONGITUDINAL & LATERAL STABILITY REQUIRED FOR LWR • WITH ELASTIC FASTENING, IT CAN MAINTAIN GAUGE AND ALIGNMENT PROPERLY, HENCE MORE SAFE • FLAT BOTTOM –SUITES MECH. TAMPING • COST EFFECTIVE • DURABLE--IMMUNE TO TERMITE, FIRE, RUSTS, ETC. • ANTI THEFT & ANTI-SABOTAGE • SUITED FOR TRACK CIRCUITING
- 35. DISADVANTAGES OF PSC SLEEPERS LAYING & HANDLING IS DIFFICULT AS IT IS HEAVY DIFFICULT TO RESTORE TRAFFIC AFTER ACCIDENT NOT AMENABLE TO MANUAL LAYING OR MAINT. REQUIRES MORE BALLAST AND WIDER FORMATION NO SCRAP VALUE- DIFFICULT TO DISPOSE MAINTENANCE OF JOINT IS DIFFICULT NOT UNIVERSAL --USE OF DIFF. TYPE OF SLEEPERS
- 36. FUNCTIONS OF SLEEPER ASSEMBALY • TRANSMIT AXLE LOAD OF VEHICLES TO BALLAST PROPERLY • HOLD – GAUGE – LEVEL – ALIGNMENT • PROVIDING LONGITUDINAL & LATERAL STABILITY TO TRACK
- 37. Fishplate – To provide continuity across rail joint for the movement of railway vehicles – Rail ends are connected by “fishplates” & “fish bolt” 37
- 38. FASTENINGS • Fixing arrangement for Rails and sleepers • Various types • Depending on type of Rails & Sleepers, 38
- 39. FASTENING • UIC ORE DEFINITION – FASTENINGS OR FASTENING DEVICES ARE DESIGNED AS THAT ASSEMBLY OF PARTS , ENSURING THE CONNECTION BETWEEN RAILS AND SLEEPERS OR RAIL BEARERS IN THE CASE OF TRADITIONAL TRACK LAYING SYSTEM OR WITH SUBSTRUCTURE IN CASE THE TRACK IS LAID DIRECTLY ON THE STRUCTURES OR ON THE TUNNEL BASE.
- 40. FASTENING TYPES • VARIOUS TYPES –RAIL FREE –RIGID –ELASTIC
- 41. FASTENING (FORCES) • FORCES IN TRACK – DOWNWARD FORCES: SLEEPER UNDER LOAD,THERE WILL BE A TENDENCY OF GAP BETWEEN RAIL AND FASTENING - FASTENING PREVENTS THIS – UPWARD FORCES: LOAD AWAY FROM SLEEPER, TRACK TENDS TO LIFT UPWARD,GAP BETWEEN RAIL AND SLEEPER – FASTENING PREVENT THIS
- 42. FASTENING (FORCES) – ROTATION OF SLEEPERS: ROTATION OF SLEEPERS ABOUT ITS OWN AXIS - FASTENING TO PREVENT THIS – LATERAL FORCES: DUE TO PARASITIC MOTIONS AND DUE TO LONGITUDINAL COMPRESSION(DURING BUCKLING)– RAIL HAS TENDENCY TO MOVE LATERALLY ON SLEEPER AND SOMETIME COMPLETE TRACK MOVE LATERALLY-FASTENING SHOULD PROVIDE BUCKLING STRENGTH AND TORSIONAL STRENGTH
- 43. FASTENING (FORCES) • LONGITUDINAL FORCES: CAUSED BY THERMAL STRESSES,WAVE ACTION AND ADHESION BETWEEN RAIL AND WHEEL.THESE FORCES MAY CAUSE MOVEMENT OF RAIL OVER SLEEPER OR MOVEMENT OF ENTIRE RAIL/SLEEPER ASSEMBLY--FASTENING SHOULD PREVENT THIS. DOWNWARD LOAD ON TOE OF RAIL CAUSED BY ELASTIC FASTENING IS CALLED TOE LOAD.
- 44. FASTENING (FORCES) – VIBRATIONS- LOW FREQUENCY DUE TO PARASITIC MOTION and VERY HIGH FREQUENCY VIBRATIONS IN VERTICAL PLANE DUE TO RAIL WHEEL INTERACTION 700 TO 1200 CPS AND AMPLITUDE OF 0.1 MM TO 0.3 MM WITH ACCELRATION OF 70 TO 100 g
- 45. EFFECTS OF VERY HIGH FREQUENCY VIBRATIONS – CAUSE OF FATIGUE FAILURE – LOOSENING OF FASTENING – LOOSENING OF BALLAST – LOSS OF TOE LOAD – EFFECT ON ROLLING STOCK – RAIL CORRUGATION THE FASTENING SHOULD ABSORB AND DAMP THE HIGH ENERGY VIBRATIONS.
- 46. ELASTIC FASTENING • RAIL IS CONNECTED WITH SLEEPER THROUGH AN ELASTIC MEDIUM, SUCH THAT IT ABSORBS ENERGY OF VIBRATIONS AND DOES NOT ALLOW TO CAUSE GAP BETWEEN RAIL AND SLEEPERS. • THERE SHOULD BE DAMPED ELASTIC SUSPENSION WITHOUT PLAY. THE FASTENING PERMITS THE MOVEMENT OF RAIL WITHOUT CAUSING ANY GAP.
- 47. TYPE OF ELASTIC FASTENING • TYPE I – IN WHICH TOE LOAD IS DERIVED FROM A FRICTIONAL GRIP OR NAILING EFFECT • ERS, DS 18 AND MACBETH • TYPE II – IN WHICH LOAD APPLICATION IS OBTAINED THROUGH A SCREW THREAD • HM, NABLA, VASSLOH • TYPE III – IN WHICH THE LOAD IS PREDETERMINED AT THE DESIGN STAGE • PENDROL
- 48. OBJECTIVES OF ELASTIC FASTENING • ELASTIC RUBBER PAD • ABSORBS SHOCKS AND DAMP OUT VIBRATIONS • INCREASE FRICTIONAL RESISTANCE TO LONG. OR LATERAL MOVEMENT OF RAIL. • DISTRIBUTE LOAD UNIFORMLY OVER SLEEPER • PROVIDE ELECTRIC INSULATION BETWEEN RAIL AND SLEEPER • REDUCE NOISE LEVEL
- 49. MECHANISM Weight of rail Source of Vibration Vibration blocked by fastening spring Rail Fastening GRP Sleeper Ballast Wt of sleeper Vibration absorbed by rubber pad Vibration absorbed By stone friction & Spring action
- 50. MECHANISM LOAD ENERGY ABSORBED ERC & GRP 60 % BALLAST 25% FORMATION 15%
- 51. VOSSLOH FASTENING Sleeper screw in dowel Tension clamps Guide plate Rail Pad
- 52. COMPARISION BETWEEN ELASTIC FASTENING TYPE II (BOLTED FASTENER) TYPE III ( CAST IN ANCHORAGE FASTENER) THREADED ELEMENT APPLYING ANCHORAGE FIXED AT THE TIME FORCE TO A SPRING STEEL OF CASTING ELEMENT THREADED ELEMENT IS -------REMOVABLE RUBBER PAD BETWEEN RAIL RUBBER PAD BETWEEN RAIL AND AND SLEEPER SLEEPER TOE LOAD GENERATED BY NO SUCH PROVISION TIGHTENING NUT ADJUSTABLE TOE LOAD FIXED TOE LOAD ALLOWS REPLACEMENT OF CASTING ANCHORAGES CANNOT ALL THE COMPONENTS IN THE BE RENEWED EVENT OF DAMAGE OILING OF THREADS ONCE IN 3 NO NEED.FIT AND FORGET TYPE YEARS
- 53. REQUIREMENT OF TOE LOAD • ERC MARK III HAS AV. TOE LOAD OF 1000 KG UNDER 12 MM. DEFLECTION. – THE AV. STATIC TOE LOAD =1000x4 =4000 KG. ASSUMING 0.5 AS COEFF. OF FRICTION BETWEEN RUBBER PAD AND RAIL, THE RAIL TO SLEEPER RESISTANCE IS APPROX. 2000 KG. – THIS IS > AV. SLEEPER TO BALLAST RESISTANCE ( 1000 KG.). SO THE CHANCES OF RELATIVE RAIL TO SLEEPER MOVEMENT ARE LESS.
- 54. WHY GREASING? LOADED CONDITION AXLELOAD 22 Tons FREE CONDITION FREE CONDITION TOE LOAD 850-1100Kg TOE LOAD 850-1100Kg Minimum Compressive stress Maximum Compressive stress Minimum Compressive stress
- 55. WHY GREASING? Figure shows the torsional force exerted due to corrosion. Torsional Force ERC ERC CORROSION Torsional Force LINER INSERT PSC
- 56. WHY GREASING? CORROSION End of function life Rate of corrosion Jamming of ERC Reduction of strength Loss of Toe Load End of function Life Life cycle Time
- 57. RUBBER PAD • FUNCTIONS – – – DAMPING OF HIGH FREQUENCY VIBRATIONS VIBRATIONALLY ISOLATE RAIL PREVENT GAP THE MECHANISM FOR ACHIEVING THIS IS – MOLECULES BROUGHT CLOSER UNDER FORCE, ENERGY DISSIPATION WHEN FORCE IS REMOVED. DAMPING IS BEST WHEN RESTRAINING FORCE IS PREPORTIONAL TO AMPLITUDE OF VIBRATION.
- 58. RUBBER PAD • COMMON TYPE OF PADS – PIMPLE TYPE PADS – GROOVED TYPE PADS • THICKNESS 6 MM
- 59. LOAD DEFLECTION CHARACTERSTICS 25 SOLID PAD PRESSURE ON RAIL(T) 20 15 GROOVED PAD 10 5 0 0 10 20 30 40 50 DEFLECTION 1/100 MM 60
- 60. RUBBER PAD • MATERIAL – NATURAL RUBBER – RIBBED SMOKED SHEET – BLEND OF STYRENE RUBBER/ POLY BUTADIENE RUBBER
- 61. RUBBER PAD • THE TOP SURFACE OF RUBBER PAD, WHICH COMES DIRECTLY IN CONTACT WITH RAIL, EXECUTE VERY HIGH FREQUENCY 1000 Hz (LOW AMPLITUDE 0.05- 0.1 mm) VIBRATIONS. • WHILE THE BOTTOM SURFACE, WHICH COMES IN CONTACT WITH SLEEPER, EXECUTE LOW FREQUENCY 20 Hz VIBRATIONS.
- 62. RUBBER PAD • FOR IMPROVING THE PERFORMANCE OF RUBBER PAD , MATERIAL SHOULD BE WITH VARYING ELASTIC PROPERTIES. • SO THE TOP OF RUBBER PAD SHOULD HAVE HIGHER MODULUS OF ELASTICITY( HARDER) WHILE BOTTOM SHOULD BE OF SOFTER MATERIAL.
- 63. LINERS – DISTRIBUTION OF TOE LOAD OVER LARGER AREA ON RAIL FOOT – ALLOW FLEXIBILITY FOR USE OF DIFFERENT RAIL SECTION ON THE SAME/ COMMON SLEEPER – PERMITS GAUGE ADJUSTMENT IN CURVED TRACK AND CORRECTION IN ALIGNMENT – PROVIDE INSULATION BETWEEN RAIL AND INSERT
- 64. LINERS • THE REQUIREMENTS OF LINER – THE LINER SHOULD HAVE PROPER SLOPE TO MATCH WITH RAIL FOOT SLOPE – THE VERTICAL LEG OF LINER SHOULD FIT PROPERLY BETWEEN RAIL AND MCI INSERT TO MAINTAIN GAUGE – IT SHOULD BE EASY TO FIX & MANUFACTURE
- 65. INSERTS • IT IS EMBEDDED IN CONCRETE AT THE TIME OF CASTING • THIS IS ANCHORAGE FOR ERC • GRIPS THE CLIP EFFECTIVELY • PROVIDES LATERAL SUPPORT TO RAIL • SHOULD HAVE ADEQUATE PULL STRENGTH (MORE THAN 10T)
- 66. INSERTS • TOE LOAD IS FUNCTION OF DIA. OF HOLE AND DIFFERENCE BETWEEN APEX OF HOLE AND TOP OF SHOULDER • CORRECT POSITIONING IS IMPORTANT – VERTICAL POSITIONING FOR TOE LOAD – LATERAL POSITIONING FOR GAUGE • THE GAP BETWEEN TOE AND RAIL SEAT SURFACE SHOULD BE 8 MM.
- 67. MAINTENANCE OF RAIL JOINTS ON CONCRETE SLEEPERS • RAIL JOINTS TO HAVE 1 M. LONG FISHPLATE • RUBBER PAD OF THE JOINT & SHOULDER SLEEPERS TO BE RENEWED EVERY YEAR • CRIB & SHOULDER BALLAST AROUND THE JOINT TO BE SCREENED EVERY YEAR • THE FISH PLATE SHOULD BE GROUND TO ACCOMMODATE ELASTIC RAIL CLIP / PROVIDE JCLIP
- 68. Thank You