Magazine

Track CompendiumFormation, Permanent Way,Maintenance, Economics

Bernhard Lichtberger

Track CompendiumFormation, Permanent Way,Maintenance, Economics

Dr. Bernhard Lichtberger

pressprpressessEuEuEurail

This book is dedicated to my dear late father Wilhelmand to my mentors,

Mr. Josef Theurer andMr. Egon Schubert

who taught me so much.

1st edition 2005, ISBN 3-7771-0320-9This publication is protected by copyright. It may not be exploited, in whole or inpart, without the approval of the publisher. This applies in particular to any form ofreproduction, translation, microfilming, and incorporation and processing in electronicsystems.© 2005 Eurailpress Tetzlaff-Hestra GmbH & Co. KGPostfach 101609, Nordkanalstraße 36, D-20097 HamburgPrinted in GermanyProduction: Verlagsdruckerei Kessler, 86399 Bobingen

Acknowledgements

I want to thank Roland Hogl who helped me to work out the illustrations. My thanks are also dueto Lothar Marx, Rainer Wenty, Helmut Misar, Johann Dumser, Leopold Frühwirt, Alf Lichtberger,Markus Schnetz, Michael Malacek, Leopold Gruber, Johann Kohel, Jürgen Dehne, Klaus Riess-berger and many others not mentioned here by name who helped me with their suggestions andmaterials.

Special thanks are due to Kornelia Haindl, my partner, who has supported me with great under-standing and encouragement.

This present voluminous book came into being from my – not quite unselfish – wish to draw upa compendium in a compressed form containing relevant data concerning track for the railwayengineer. Many ideas, as well as the basis of my comprehension of physical laws relevant fortrack and track maintenance, were acquired from my dear friend Egon Schubert, who unfortun-ately died much too early, and Josef Theurer, for which I am indebted. My work as the head ofthe research & development department of Plasser & Theurer has offered and still offers me theopportunity to deal with research in the field of track behaviour and optimum track maintenancemethods. This knowledge and the rich experience gained on my job during the past eighteenyears have been worked into this book. The present compendium also contains many interestingfacts from relevant publications. I owe thanks and respect also to these numerous authors whocannot be mentioned here.

This book has been translated with great precision by Ursula Stampfer. I am greatly indebted toher for this exemplary work.

My colleague Norbert Jurasek has gone to great lengths to check the technical terms used andthe general correctness of the English version. I would like to thank him for his wholeheartedcommitment and the many hours spent on this work. The ensuing high standard of the Englishversion could not have been reached without his assistance.

Compared to the 1st and 2nd German editions, the present English version contains several prin-cipal amendments and additions. They concern the basis of catenary and catenary construction,as well as their maintenance, and furthermore, the most recent findings about the developmentof head checks and the latest practical results of tests of the resistance of head-hardened railsto wear have been included.

This English edition also contains the theory of dynamic track stabilising, additional findings onthe capacities of ballast cleaners and the connection between screening quality and degree ofrecycling. Furthermore, additions have been made in the chapters “interaction between wheeland rail” and “economics”.

I hope that this work will be a help and useful reference not only for the present generation ofrailway engineers, but also for those in the future.

In this way I hope to have made a small contribution to a successful railway.

Bernhard Lichtberger Linz, im Februar 2005

Overview

1 General information ................................................................................ 28

2 The track structure .................................................................................. 32

2.1 Track installation conditions ...................................................................... 332.2 Static forces on the track ........................................................................... 422.3 Dynamic forces on the track ...................................................................... 462.4 Track resistance .......................................................................................... 472.5 Track calculation ......................................................................................... 602.6 Modern track calculation considering dynamic effects .......................... 712.7 Stable track grid support ........................................................................... 722.8 The track deformation energy ................................................................... 962.9 Conclusions on track maintenance ........................................................... 972.10 Maintenance measures .............................................................................. 97

3 The rails ...................................................................................................... 99

3.1 Rail requirements ........................................................................................ 993.2 Rail production ............................................................................................ 993.3 Types of rails ................................................................................................ 1003.4 Chemical composition of rail steel ............................................................ 1053.5 Static hardness test .................................................................................... 1053.6 Stress-strain diagram ................................................................................. 1063.7 Rail branding ................................................................................................ 1073.8 Rail forms ..................................................................................................... 1073.9 Rail lengths .................................................................................................. 1133.10 Noise emission of rails ............................................................................... 1133.11 Rail stress .................................................................................................... 1133.12 Ultrasonic rail test ....................................................................................... 1143.13 Quenching and tempering of rails ............................................................. 1193.14 Rail calculation ............................................................................................ 1193.15 Wear behaviour of wheel and rail steel ..................................................... 1203.16 Rail welding ................................................................................................. 1233.17 Laying, welding and tensioning of rails .................................................... 1283.18 Rail defects .................................................................................................. 1313.19 Rail Treatment in the track ......................................................................... 145

4 Rail fastenings .......................................................................................... 147

4.1 The CEN standard on rail fastenings ........................................................ 1474.2 The purpose of the rail fastenings ............................................................ 1474.3 The effective forces .................................................................................... 1484.4 Differences between rigid / elastic rail fastenings .................................. 1504.5 The rail pads ................................................................................................ 1514.6 The design of rail fastenings ...................................................................... 1534.7 Checking the rail connections ................................................................... 1664.8 Checking rail fastenings by the GRMS track recording car ................... 166

Overview

5

5 The sleepers .............................................................................................. 167

5.1 Comparison between wooden and concrete sleepers ........................... 1675.2 The purpose of sleepers ............................................................................. 1685.3 Wooden sleepers ......................................................................................... 1685.4 Steel sleepers .............................................................................................. 1725.5 Reinforced concrete sleepers .................................................................... 1765.6 Sleeper calculation ...................................................................................... 1845.7 Resistance to lateral and longitudinal displacement .............................. 188

6 Ballast and ballast bed ........................................................................... 189

6.1 Ballast bed requirements ........................................................................... 1896.2 Physical properties of ballast ..................................................................... 1986.3 Ballast Cleaning ........................................................................................... 2026.4 Ballast bed dimensioning ........................................................................... 2026.5 Restoration of the ballast bed ................................................................... 2046.6 Conglutination of ballast ............................................................................ 207

7 The track formation ................................................................................. 209

7.1 General information on the bearing capacity of the track ...................... 2097.2 Drainage of the formation .......................................................................... 2107.3 Reinforcement of the formation ................................................................ 210

8 The Subsoil ................................................................................................ 232

8.1 Types of soils and their parameters .......................................................... 2328.2 Properties of soils ....................................................................................... 2378.3 Defects of the soil formation ..................................................................... 2428.4 Reasons for damage to the soil formation ............................................... 2438.5 Consequences of damage to the soil formation ...................................... 2438.6 Ideal and poor soils ..................................................................................... 2448.7 Stress on the subsoil and its settlement behaviour ................................ 2448.8 Subsoil and earth structure deformations ................................................ 2488.9 Load on the soil formation ......................................................................... 2498.10 Geometrical requirements for the soil formation .................................... 2508.11 Soil analyses ................................................................................................ 2518.12 Soil improvement and compaction ........................................................... 2528.13 Chemical soil conversion ........................................................................... 2548.14 Soil drainage ................................................................................................ 2558.15 Frost sensitivity of the subsoil ................................................................... 258

9 The ballasted track .................................................................................. 260

9.1 Approaches to describe track quality ....................................................... 2609.2 Properties of track quality .......................................................................... 2619.3 Properties of the ballasted track ............................................................... 2649.4 Course of pressure in the substructure below the sleeper .................... 2709.5 The deformation behaviour of ballasted track ......................................... 2729.6 Critical vibration speed and dynamic settlement behaviour .................. 2809.7 The bearing capacity of the ballast bed ................................................... 283

Overview

6

9.8 The resistance of the ballasted track to lateral displacement ............... 2909.9 The critical speed of the permanent way ................................................. 2909.10 Reasons for the development of fines ...................................................... 2929.11 Distribution of fines in the ballast bed ...................................................... 2939.12 In search of an optimum track structure .................................................. 2949.13 How to produce track of highest initial quality ........................................ 2979.14 Ballasted tracks with cross sleepers ........................................................ 2989.15 Ballasted track for high-speed lines ......................................................... 299

10 The slab track ........................................................................................... 309

10.1 Requirements of slab track ........................................................................ 30910.2 The slab track in tunnels ............................................................................ 31210.3 The slab track on earth structures ............................................................ 31210.4 Comparison between ballasted track / slab track .................................. 31210.5 Economic efficiency and cost of the slab track ...................................... 31510.6 Design types of slab track ......................................................................... 31510.7 Comparison of overall heights of various designs of slab track ........... 33010.8 Technical and economic comparison of the slab track designs ............ 331

11 Interaction between wheel and rail .................................................... 333

11.1 Dynamics of vehicle movement ................................................................. 33311.2 The contact between wheel and rail ......................................................... 33911.3 The influence of the rail / wheel contact geometry ................................. 34211.4 Vehicle defects ............................................................................................ 34211.5 Forces acting on the track due to dynamic wheel loads ........................ 34311.6 Rail vehicle noise ........................................................................................ 35111.7 Assessment and measurement of vehicle reactions ............................... 35511.8 The requirements of the track for the vehicle .......................................... 35611.9 The optimum vehicle ................................................................................... 35611.10 Tilting trains ................................................................................................. 36011.11 Vehicle monitoring ...................................................................................... 361

12 The switches ............................................................................................. 363

12.1 The tasks of switches, crossings and diamond crossings with slips ... 36312.2 The main types of switches, crossings and diamond crossings

with slips ...................................................................................................... 36312.3 Designation of switches ............................................................................. 36512.4 Elements of switches .................................................................................. 36612.5 The vibration-damped switch with divided long sleepers ...................... 37612.6 Geometric and structural characteristics of switches ............................ 37712.7 Schematic representation of switches ..................................................... 37912.8 Settlement behaviour of switches ............................................................. 37912.9 Maintenance of switches ........................................................................... 37912.10 Overlaps of rails .......................................................................................... 381

13 Overhead line system ............................................................................. 385

13.1 Types of traction current ............................................................................ 38513.2 Direct current systems (DC) ....................................................................... 387

Overview

7

13.3 Alternating current systems (AC) .............................................................. 38713.4 Catenary ....................................................................................................... 38713.5 Air distances ................................................................................................ 39013.6 Various designs of overhead lines ............................................................. 39013.7 Structure of longitudinal catenary ............................................................. 39213.8 Return of traction current .......................................................................... 39513.9 Admissible contact voltage ........................................................................ 39613.10 Interaction between current collectors and overhead line ..................... 397

14 Fundamentals on guiding and signalling in railway operation .... 398

14.1 Block sections ............................................................................................. 39814.2 Track circuits ............................................................................................... 39814.3 Axle counters ............................................................................................... 39814.4 Intermittent automatic train control .......................................................... 39914.5 Continuous train control (CTC) .................................................................. 40014.6 The European rail traffic management system ERTMS .......................... 40014.7 Automatic train stop ................................................................................... 40114.8 Hot box detection ........................................................................................ 401

15 Track maintenance .................................................................................. 402

15.1 Typical maintenance cycles ....................................................................... 40215.2 Standard values for maintenance and danger limits ............................... 40215.3 Accuracy of acceptance ............................................................................. 40515.4 Considerations on the track quality .......................................................... 40615.5 The choice of the optimum duration of track possessions .................... 41315.6 Correction of track geometry .................................................................... 41415.7 Correction of rail defects ........................................................................... 50115.8 Ballast bed treatment ................................................................................. 52015.9 Subsoil improvement .................................................................................. 55615.10 Laying and relaying of the track grid ........................................................ 56815.11 Laying and transportation of switches ..................................................... 57415.12 Track construction cranes ......................................................................... 57615.13 Maintenance of overhead lines .................................................................. 577

16 Life cycle costs of railways ................................................................... 585

16.1 UIC-study comparing the LCC of railways ............................................... 58516.2 Factors forcing up costs ............................................................................ 58716.3 Cost saving potentials ................................................................................ 58816.4 Differential LCC ........................................................................................... 58916.5 Track maintenance costs ........................................................................... 59416.6 The effect of mechanisation on the economic efficiency

of permanent-way maintenance ................................................................ 59416.7 Track access charges ................................................................................. 595

Literature .................................................................................................... 597

Keywords ................................................................................................... 624

Advertisers’ Index .................................................................................... 634

Overview

8

Contents

1 General information ................................................................................ 28

2 The track structure .................................................................................. 32

2.1 Track installation conditions ...................................................................... 332.1.1 Circular curve and tangent track ..................................................................... 342.1.2 Superelevation ................................................................................................ 342.1.3 Laying inclination and nominal track gauge of the rails ................................... 362.1.4 Track widening ............................................................................................... 372.1.5 Transition Curves ............................................................................................ 372.1.6 Superelevation Ramps..................................................................................... 382.1.7 Longitudinal inclination and changes in gradient ............................................. 392.1.8 Line cross sections on soil formation .............................................................. 392.1.9 Track cross sections ....................................................................................... 402.1.10 Formation widths ............................................................................................ 402.1.11 Critical speeds for heavy permanent way ....................................................... 412.1.12 Maximum speed on various railways .............................................................. 412.2 Static forces on the track ........................................................................... 422.2.1 Vertical forces ................................................................................................. 422.2.2 Longitudinal rail forces .................................................................................... 422.2.2.1 Acceleration and braking forces ..................................................................... 432.2.3 Lateral forces .................................................................................................. 432.3 Dynamic forces on the track ...................................................................... 462.3.1 Wheel load transfers ....................................................................................... 462.3.2 Vibration excitations ....................................................................................... 462.3.3 Natural vehicle and track oscillations .............................................................. 462.3.3.1 Natural vehicle oscillations .............................................................................. 462.3.3.2 Permanent-way natural oscillation .................................................................. 462.4 Track resistance .......................................................................................... 472.4.1 Bearing capacity ............................................................................................. 472.4.2 Coefficient of ballast C and vertical rigidity ...................................................... 482.4.3 Longitudinal resistance ................................................................................... 532.4.3.1 Fishplate friction resistance ............................................................................. 532.4.3.2 Longitudinal displacement resistance ............................................................. 532.4.3.3 Creep resistance ............................................................................................ 542.4.4 Lateral displacement resistance ...................................................................... 542.4.4.1 Methods of lateral displacement resistance measurements ............................ 542.4.4.2 Lateral displacement resistance depending on the track structure condition ... 562.4.4.3 Parameters influencing lateral displacement resistance .................................. 572.4.4.4 Composition of lateral displacement resistance .............................................. 582.4.4.5 Lateral displacement resistance of various sleeper types ................................ 592.4.4.6 Lateral displacement resistance of various ballast types ................................. 592.4.5 The distribution of force from wheel to subsoil ............................................... 592.5 Track calculation ......................................................................................... 602.5.1 Rail calculation ............................................................................................... 612.5.1.1 Calculation of rail foot tension ......................................................................... 622.5.1.2 Rail head stress calculation ............................................................................ 66

Contents

9

2.5.1.3 Admissible rail stress when operating permanent-way machinery .................. 672.5.2 Sleeper calculation ......................................................................................... 702.5.3 Rail fastening calculation ................................................................................ 702.5.4 Limit values of ballast loads ............................................................................ 702.6 Modern track calculation considering dynamic effects .......................... 712.7 Stable track grid support ........................................................................... 722.7.1 Curve breathing .............................................................................................. 742.7.2 The Prud’homme criterion .............................................................................. 742.7.3 Rail temperature versus rail fastening down temperature ................................ 762.7.3.1 Long welded rails ........................................................................................... 772.7.4 Calculation of horizontal position stability in tangent track .............................. 782.7.5 Calculation of horizontal position stability in curves ......................................... 792.7.6 Calculation of vertical position stability ............................................................ 802.7.7 Longitudinal track stability .............................................................................. 812.7.7.1 Longitudinal movements in case of great longitudinal forces .......................... 822.7.7.2 Longitudinal movement in case of small longitudinal forces ............................ 822.7.8 Natural vibration of bridges ............................................................................. 832.7.9 Sliding layer – embankment ............................................................................ 842.7.10 Environmental problems caused by tracks ..................................................... 842.7.11 Behaviour of natural frequencies ..................................................................... 852.7.12 Propagation of oscillation ............................................................................... 892.7.13 Influence of railways on the environment ........................................................ 942.7.14 Measures to reduce environmental influence .................................................. 952.8 The track deformation energy ................................................................... 962.9 Conclusions on track maintenance ........................................................... 972.10 Maintenance measures .............................................................................. 97

3 The rails ...................................................................................................... 99

3.1 Rail requirements ........................................................................................ 993.2 Rail production ............................................................................................ 993.3 Types of rails ................................................................................................ 1003.3.1 “Naturally” hard rails ....................................................................................... 1003.3.2 Thermally treated rails ..................................................................................... 1003.3.3 High-alloy rails ................................................................................................ 1043.3.4 Bainitic rails .................................................................................................... 1043.4 Chemical composition of rail steel ............................................................ 1053.5 Static hardness test .................................................................................... 1053.5.1 Brinell hardness .............................................................................................. 1063.5.2 Diamond pyramid hardness ............................................................................ 1063.5.3 Rockwell hardness ......................................................................................... 1063.6 Stress-strain diagram ................................................................................. 1063.7 Rail branding ................................................................................................ 1073.8 Rail forms ..................................................................................................... 1073.8.1 Unsymmetrical rail profiles in narrow radii ....................................................... 1113.9 Rail lengths .................................................................................................. 1133.10 Noise emission of rails ............................................................................... 1133.11 Rail stress .................................................................................................... 1133.11.1 Stress by vertical wheel load .......................................................................... 1133.11.1.1 Rolling contact fatigue on rails ........................................................................ 113

Contents

10

3.11.1.2 Cracks in the rail head (shells and taches ovales) ........................................... 1143.11.1.3 Cracks on the rail surface (head checks, spalling and squats) ........................ 1143.12 Ultrasonic rail test ....................................................................................... 1143.12.1 Stress caused by guiding forces ..................................................................... 1143.12.2 Stress caused by dynamic forces ................................................................... 1153.12.2.1 Wheel flats ...................................................................................................... 1153.12.2.2 Dynamic forces caused by surface defects .................................................... 1153.12.3 Longitudinal forces caused by changes in temperature .................................. 1153.12.4 Longitudinal forces caused by driving and braking forces ............................... 1153.12.5 Stress in the rail .............................................................................................. 1163.12.5.1 Internal rail stress ........................................................................................... 1163.12.5.2 Hertz’ surface pressure .................................................................................. 1173.12.6 Spring deflection of the rail head .................................................................... 1173.12.7 Stress caused by permanent-way vehicles ..................................................... 1183.13 Quenching and tempering of rails ............................................................. 1193.13.1 Rail hardening ................................................................................................ 1193.13.2 Rail surface treatment ..................................................................................... 1193.13.2.1 Laser hardening .............................................................................................. 1193.13.2.2 Plasma coating ............................................................................................... 1193.13.2.3 Laser coating ................................................................................................. 1193.14 Rail calculation ............................................................................................ 1193.15 Wear behaviour of wheel and rail steel ..................................................... 1203.15.1 The magic wear rate ....................................................................................... 1203.15.2 Lateral rail wear .............................................................................................. 1223.15.3 Vertical rail wear ............................................................................................. 1233.16 Rail welding ................................................................................................. 1233.16.1 Aluminothermic welding .................................................................................. 1233.16.2 Flash-butt welding .......................................................................................... 1243.16.2.1 The mobile flash-butt welding machine .......................................................... 1253.16.3 Rail fractures in welds ..................................................................................... 1253.17 Laying, welding and tensioning of rails .................................................... 1283.17.1 Neutral temperature ........................................................................................ 1283.17.2 Production of long welded tracks ................................................................... 1293.17.3 Temperature increase by linear eddy current brakes ....................................... 1313.18 Rail defects .................................................................................................. 1313.18.1 Rolling-contact fatigue and wear .................................................................... 1313.18.2 Head checks .................................................................................................. 1343.18.3 Belgrospis ...................................................................................................... 1363.18.4 Squats ............................................................................................................ 1373.18.5 Damage to running edges of single-track lines ............................................... 1373.18.6 Indentations .................................................................................................... 1373.18.6.1 Periodical indentations .................................................................................... 1373.18.6.2 Irregular indentations (brown spots) ................................................................ 1373.18.7 Wheel burns ................................................................................................... 1373.18.8 Skid marks – short waves .............................................................................. 1373.18.9 Corrugation .................................................................................................... 1383.18.9.1 Types of corrugations ..................................................................................... 1393.18.9.1.1 Heavy haul corrugations ................................................................................. 1403.18.9.1.2 Light rail corrugations ..................................................................................... 140

Contents

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3.18.9.1.3 Rolling contact fatigue (RCF) corrugations ...................................................... 1403.18.9.1.4 Booted sleeper corrugations .......................................................................... 1413.18.9.1.5 Rutting corrugations ....................................................................................... 1413.18.9.1.6 Roaring rail corrugation .................................................................................. 1413.18.9.2 Growth of corrugations ................................................................................... 1423.18.10 Rolling defects ................................................................................................ 1423.18.11 Triggers and growth of cracks ........................................................................ 1423.18.12 Measurement of rail wear ............................................................................... 1443.19 Rail Treatment in the track ......................................................................... 1453.19.1 Treatment of low rail joints .............................................................................. 1453.19.2 Treatment of corrugations and skid marks ...................................................... 1453.19.2.1 Rail head planing true to profile ...................................................................... 1453.19.2.2 Grinding by rotating abrasive disks ................................................................. 1453.19.2.3 Oscillating grinding ......................................................................................... 145

4 Rail fastenings .......................................................................................... 147

4.1 The CEN standard on rail fastenings ........................................................ 1474.1.1 Rail fastening requirements ............................................................................. 1474.1.1.1 Rail creep force .............................................................................................. 1474.1.1.2 Torsional test .................................................................................................. 1474.1.1.3 Damping of impact loads ............................................................................... 1474.1.1.4 Permanent load measurement ........................................................................ 1474.2 The purpose of the rail fastenings ............................................................ 1474.3 The effective forces .................................................................................... 1484.3.1 Vertical forces ................................................................................................. 1484.3.2 Lateral forces (acting across the track) ........................................................... 1484.3.2.1 Track gauge widening .................................................................................... 1484.3.3 Forces acting in the longitudinal track direction .............................................. 1504.4 Differences between rigid / elastic rail fastenings .................................. 1504.5 The rail pads ................................................................................................ 1514.6 The design of rail fastenings ...................................................................... 1534.6.1 Rail fastening to wooden sleepers .................................................................. 1534.6.1.1 The direct fastening to wooden sleepers ........................................................ 1534.6.1.2 The indirect fastening to wooden sleepers ..................................................... 1544.6.1.2.1 Vossloh permanent way KS with Skl12 clip .................................................... 1544.6.1.2.2 K permanent way ........................................................................................... 1544.6.2 The rail fastening to steel sleepers .................................................................. 1564.6.2.1 The direct fastening to steel sleepers ............................................................. 1564.6.3 The rail fastening to concrete sleepers ........................................................... 1564.6.3.1 The direct fastening to concrete sleepers ....................................................... 1564.6.3.1.1 FIST fastening ................................................................................................ 1564.6.3.1.2 Pandrol fastening ........................................................................................... 1564.6.3.1.2.1 Pandrol fastclip ............................................................................................... 1564.6.3.1.2.2 Pandrol e-clip ................................................................................................. 1584.6.3.1.3 Vossloh fastening ........................................................................................... 1584.6.3.1.3.1 W14 permanent way with Skl14 clip ............................................................... 1584.6.3.1.3.2 300 Permanent way with Skl15 clip ................................................................ 1584.6.3.1.4 Nabla fastening .............................................................................................. 1584.6.3.1.5 Elastic spike fastening .................................................................................... 160

Contents

12

4.6.3.2 The indirect fastening to concrete sleepers .................................................... 1624.6.3.3 Anti-creep devices .......................................................................................... 1624.6.3.4 Sleeper Anchors ............................................................................................. 1634.6.3.5 Safety caps .................................................................................................... 1634.6.4 Rail connections ............................................................................................. 1634.6.4.1 Rail connections, suspended joints ................................................................ 1634.6.4.2 Rail connections, supported joints .................................................................. 1644.6.4.3 Rail connections, temporary joints .................................................................. 1654.7 Checking the rail connections ................................................................... 1664.8 Checking rail fastenings by the GRMS track recording car ................... 166

5 The sleepers .............................................................................................. 167

5.1 Comparison between wooden and concrete sleepers ........................... 1675.2 The purpose of sleepers ............................................................................. 1685.3 Wooden sleepers ......................................................................................... 1685.3.1 The treatment of wooden sleepers ................................................................. 1705.3.2 Defects of wooden sleepers ........................................................................... 1705.3.3 Maintenance of wooden sleepers in the track ................................................ 1705.3.3.1 Cyclic renewal of individual wooden sleepers (USA) ....................................... 1715.3.3.2 Total sleeper renewal (Europe) ........................................................................ 1715.3.4 The experience with wooden sleepers in the USA .......................................... 1715.3.5 Hardwood and softwood ................................................................................ 1725.4 Steel sleepers .............................................................................................. 1725.4.1 Tensile test ..................................................................................................... 1725.4.2 Bending test ................................................................................................... 1725.4.3 Y Steel sleepers .............................................................................................. 1755.5 Reinforced concrete sleepers .................................................................... 1765.5.1 Approval tests and requirements for concrete sleepers .................................. 1775.5.1.1 Requirements to be met by concrete ............................................................. 1775.5.1.2 Sleeper approval tests .................................................................................... 1775.5.1.2.1 Static bending test ......................................................................................... 1775.5.1.2.2 Dynamic bending test ..................................................................................... 1775.5.1.2.3 Fatigue test .................................................................................................... 1775.5.1.2.4 Electric sleeper resistance .............................................................................. 1775.5.1.2.5 Further tests ................................................................................................... 1785.5.2 Experiences in practical application of concrete sleepers ............................... 1785.5.3 Twin-block sleepers ........................................................................................ 1785.5.3.1 Twin-block sleepers made of concrete polymer .............................................. 1785.5.4 Monoblock concrete sleepers ........................................................................ 1795.5.5 Special forms of concrete sleepers ................................................................. 1805.5.5.1 Wing sleepers ................................................................................................ 1805.5.5.2 Frame sleepers ............................................................................................... 1825.5.5.3 Wide sleepers ................................................................................................. 1835.5.5.4 The Be19ae concrete sleeper with lateral profile ............................................. 1835.5.5.5 The “soled” sleeper ........................................................................................ 1835.6 Sleeper calculation ...................................................................................... 1845.6.1 Design wheel load .......................................................................................... 1845.6.2 Calculation of cross sleepers .......................................................................... 1855.6.3 Calculation of longitudinal sleepers ................................................................. 185

Contents

13

5.6.4 Calculation of sleeper plates ........................................................................... 1865.6.5 Distribution of the wheel load ......................................................................... 1865.6.6 Sleeper sagging ............................................................................................. 1875.7 Resistance to lateral and longitudinal displacement .............................. 1885.7.1 Resistance to lateral displacement ................................................................. 1885.7.2 Resistance to longitudinal displacement ......................................................... 188

6 Ballast and ballast bed ........................................................................... 189

6.1 Ballast bed requirements ........................................................................... 1896.1.1 The ballast bed cross-section ......................................................................... 1896.1.2 Ballast materials ............................................................................................. 1906.1.2.1 Crushed ballast .............................................................................................. 1906.1.2.1.1 Grain shapes .................................................................................................. 1916.1.2.2 Round ballast ................................................................................................. 1916.1.2.3 Ballast in bags ................................................................................................ 1926.1.3 Testing of track ballast .................................................................................... 1926.1.3.1 Los Angeles-test (LA) ..................................................................................... 1926.1.3.2 Aggregate Impact Value (AIV) ......................................................................... 1936.1.3.3 The Deval test (DH) ........................................................................................ 1946.1.3.4 Resistance to impact ...................................................................................... 1946.1.3.5 Petrographic examination ............................................................................... 1946.1.3.6 Grain shape .................................................................................................... 1946.1.3.7 Resistance to weathering ............................................................................... 1956.1.4 Technical conditions for the supply of ballast track ......................................... 1956.1.5 Types of ballast contamination ........................................................................ 1966.1.5.1 Methods of evaluation of the degree of contamination ................................... 1976.1.5.1.1 The isotope method ....................................................................................... 1976.1.5.1.2 The track recording car method ..................................................................... 1976.1.5.1.3 Visual inspection ............................................................................................. 1986.1.5.1.4 The sampling test ........................................................................................... 1986.1.5.1.5 The frame test ................................................................................................ 1986.2 Physical properties of ballast ..................................................................... 1986.2.1 The shearing behaviour of ballast – the angle of internal friction ..................... 1986.2.1.1 The static shearing behaviour ......................................................................... 1986.2.1.2 Static shearing behaviour of contaminated ballast, used ballast,

round gravel and recycled ballast ................................................................... 1996.2.1.3 Static shearing behaviour with an optimum share of distance grain ................ 2006.2.1.4 Dynamic shearing behaviour ........................................................................... 2016.3 Ballast Cleaning ........................................................................................... 2026.3.1 Cleaning of the ballast bed shoulders ............................................................. 2026.3.2 Cleaning of the entire ballast bed ................................................................... 2026.3.3 The performance of cleaning machines .......................................................... 2026.3.4 Washing of ballast .......................................................................................... 2026.4 Ballast bed dimensioning ........................................................................... 2026.4.1 The optimum ballast thickness – load distribution on sleepers ....................... 2026.4.2 Ballast required for ballast beds of different cross sections ............................. 2046.5 Restoration of the ballast bed ................................................................... 2046.5.1 Restoration of track position by machines ...................................................... 204

Contents

14

6.5.2 Technology of working after ballast cleaning ................................................... 2046.5.2.1 Track tamping ................................................................................................ 2066.5.2.2 Spatial ballast consolidation ........................................................................... 2066.5.2.3 Track stabilising .............................................................................................. 2066.5.2.4 Homogenising the ballast bed ........................................................................ 2066.6 Conglutination of ballast ............................................................................ 207

7 The track formation ................................................................................. 209

7.1 General information on the bearing capacity of the track ...................... 2097.1.1 Measurement of the bearing capacity of the formation ................................... 2097.1.1.1 Plate load bearing test .................................................................................... 2097.1.1.2 Dynamic plate load device .............................................................................. 2097.1.2 Consolidation of the formation – Proctor density ............................................ 2097.2 Drainage of the formation .......................................................................... 2107.3 Reinforcement of the formation ................................................................ 2107.3.1 Reinforcement of the formation by pavements, slabs ..................................... 2107.3.2 Chemical soil transformation ........................................................................... 2117.3.3 Increased thickness of the ballast bed ............................................................ 2117.3.4 PVC sheets .................................................................................................... 2127.3.5 Insertion of protective layers ........................................................................... 2127.3.5.1 Dimensioning of the bearing layers ................................................................. 2167.3.5.1.1 Dimensioning according to the bearing capacity (formation protective layer) .. 2167.3.5.1.1.1 Modulus of natural deformation ...................................................................... 2177.3.5.1.1.2 Modulus of deformation of the earth formation ............................................... 2177.3.5.1.1.3 Dimensioning of the thickness of the formation protective layer ...................... 2187.3.5.1.1.4 Grading curve for the materials to be applied in the formation protective layer 2187.3.5.1.1.5 Proof of filter stability of the material applied in the formation protective layer . 2187.3.5.1.2 Dimensioning with respect to frost protection ................................................. 2217.3.5.1.3 Frost criterion according to Casagrande ......................................................... 2237.3.5.1.4 Frost index ...................................................................................................... 2247.3.5.1.5 Calculation of the frost penetration depth for homogeneous soil .................... 2247.3.5.1.5.1 Frost protection by thermal insulating slabs .................................................... 2267.3.5.1.6 Recommended layer thickness ....................................................................... 2267.3.6 Insertion of geotextiles .................................................................................... 2267.3.6.1 Geotextiles as separating, filtering and draining elements under

supporting layers ............................................................................................ 2287.3.6.2 Geotextiles reinforcement elements ................................................................ 2287.3.6.3 Geotextiles as a reinforcing element with additional separating and

filtering effect .................................................................................................. 2297.3.6.4 The influence of geotextiles for dimensioning the supporting system .............. 2297.3.6.5 Long-term behaviour of geotextiles ................................................................ 2297.3.6.6 Dynamic strain on geotextiles ......................................................................... 2297.3.6.7 Insertion of geotextiles between ballast and formation .................................... 2307.3.6.8 Geotextile requirements .................................................................................. 230

8 The Subsoil ................................................................................................ 232

8.1 Types of soils and their parameters .......................................................... 2328.1.1 Characteristic soil parameters ........................................................................ 232

Contents

15

8.1.1.1 Degree of irregularity U ................................................................................... 2328.1.1.2 Share of pores n and pore number e .............................................................. 2338.1.1.3 Specific gravity ............................................................................................... 2338.1.1.4 The simple Proctor test .................................................................................. 2338.1.1.5 The plate load bearing test and the modulus of deformation Ev2 ..................... 2348.1.1.6 Measurement of bearing capacity with a light drop weight device .................. 2348.1.1.7 Compaction ratio DPr ...................................................................................... 2348.1.1.8 Water content w.............................................................................................. 2348.1.1.9 Liquid limit and plastic limit per water content ................................................ 2358.1.1.10 Plastic properties ............................................................................................ 2358.1.1.11 Shear strength ................................................................................................ 2368.1.2 Parameters of bearing capacity ...................................................................... 2368.1.2.1 The coefficient of ballast C ............................................................................. 2378.1.2.2 California Bearing Ratio (CBR) ........................................................................ 2378.2 Properties of soils ....................................................................................... 2378.2.1 Moisture and density in dry conditions ........................................................... 2378.2.2 Plasticity (Atterberg limit – plastic limit) ........................................................... 2378.2.3 Tensional and expansion behaviour of soils .................................................... 2388.2.3.1 Effective tension ............................................................................................. 2388.2.3.2 The influence of pore water pressure .............................................................. 2388.2.3.3 Capillarity ........................................................................................................ 2418.2.3.4 Water percolating into the soil ........................................................................ 2418.2.4 The bearing capacity of soils .......................................................................... 2428.2.4.1 Bearing capacity and compactibility of sand and gravel ................................. 2428.2.4.2 Bearing capacity and compactibility of silt and clay ........................................ 2428.3 Defects of the soil formation ..................................................................... 2428.4 Reasons for damage to the soil formation ............................................... 2438.5 Consequences of damage to the soil formation ...................................... 2438.6 Ideal and poor soils ..................................................................................... 2448.7 Stress on the subsoil and its settlement behaviour ................................ 2448.7.1 Ballast bed modulus of multi-layer systems – the theory of Odemark ............. 2448.7.2 Diffusion of stress in multi-layer systems in the load axis ................................ 2458.7.2.1 The influence of adjacent sleepers on the compressive strains of the soil ....... 2468.7.2.2 Dynamic stability ............................................................................................ 2478.8 Subsoil and earth structure deformations ................................................ 2488.9 Load on the soil formation ......................................................................... 2498.10 Geometrical requirements for the soil formation .................................... 2508.11 Soil analyses ................................................................................................ 2518.11.1 Seismic method ............................................................................................. 2518.11.2 Slotted-probe sounding with sampling ........................................................... 2518.11.3 Subsoil testing machine (UUM) ...................................................................... 2518.11.4 Evaluation of longitudinal versine values recorded by track recording cars ..... 2518.11.5 Stiffness measurements ................................................................................. 2528.11.6 Cone penetration test – manometric capsule ................................................. 2528.11.7 Dynamic probes ............................................................................................. 2528.11.8 Prospecting slots ............................................................................................ 2528.12 Soil improvement and compaction ........................................................... 2528.12.1 Vibration pressure compaction ....................................................................... 2538.12.2 Vibration filling method ................................................................................... 253

Contents

16

8.12.3 Pile-like bearing elements ............................................................................... 2538.13 Chemical soil conversion ........................................................................... 2548.13.1 Soil improvement by lime ............................................................................... 2548.13.2 Soil stabilisation by cement ............................................................................ 2548.13.3 Soil strengthening according to Joosten ......................................................... 2548.14 Soil drainage ................................................................................................ 2558.14.1 Water in the soil .............................................................................................. 2558.14.2 The influence of water on the soil ................................................................... 2558.14.2.1 Ice lenses and frost heaps .............................................................................. 2558.14.3 Draining facilities, drainage ............................................................................. 2568.14.3.1 Open drainage facilities .................................................................................. 2568.14.3.2 Enclosed drainage facilities ............................................................................. 2578.14.3.3 Inspection pits ................................................................................................ 2578.14.3.4 Maintenance and service of drainage facilities ................................................ 2578.14.3.5 The flowing off of water .................................................................................. 2588.15 Frost sensitivity of the subsoil ................................................................... 2588.15.1 Frost criterion according to Casagrande ......................................................... 2588.15.2 Protection from frost heaves ........................................................................... 259

9 The ballasted track .................................................................................. 260

9.1 Approaches to describe track quality ....................................................... 2609.1.1 Linear representation ...................................................................................... 2619.1.2 Semi-logarithmic representation ..................................................................... 2619.2 Properties of track quality .......................................................................... 2619.2.1 Schematic course of track quality ................................................................... 2619.2.2 Initial quality .................................................................................................... 2629.2.3 Initial settlement .............................................................................................. 2629.2.4 Rate of deterioration ....................................................................................... 2629.2.4.1 Influences on the rate of deterioration ............................................................ 2639.2.4.1.1 The influence of dynamic force ....................................................................... 2639.2.4.1.2 Rail surface defects and rail profile ................................................................. 2639.2.4.1.3 Irregular sleeper spacing ................................................................................ 2639.2.4.1.4 Different sleeper support ................................................................................ 2649.2.4.1.5 Irregular ballast settlement .............................................................................. 2649.2.4.1.6 Irregular settlement of the subsoil ................................................................... 2649.3 Properties of the ballasted track ............................................................... 2649.3.1 Measurement of the course of track quality .................................................... 2669.3.1.1 The “memory” of the track ............................................................................. 2679.3.2 Improvement by tamping ................................................................................ 2699.3.3 Pressure distribution in the ballast below the sleepers .................................... 2709.4 Course of pressure in the substructure below the sleeper .................... 2709.5 The deformation behaviour of ballasted track ......................................... 2729.5.1 Track defects in a vertical direction ................................................................. 2739.5.2 Track defects in a horizontal direction ............................................................. 2739.5.3 Track defects in cross level direction .............................................................. 2749.5.4 Ballast settlement behaviour ........................................................................... 2749.5.4.1 Standard deviation of settlements – defects in the longitudinal level ............... 2749.5.4.2 Dependence of settlement on the axle load .................................................... 2759.5.4.3 Settlement and vertical dynamic track stiffness .............................................. 277

Contents

17

9.5.4.4 The ballast as multi-body system ................................................................... 2779.5.4.5 Settlement properties of different ballast materials .......................................... 2799.5.4.6 Settlement behaviour depending on the contamination of the ballast bed ...... 2809.5.4.7 The course of settlement after tamping according to Shenton ....................... 2809.6 Critical vibration speed and dynamic settlement behaviour .................. 2809.7 The bearing capacity of the ballast bed ................................................... 2839.7.1 Coefficient of ballast ....................................................................................... 2839.7.2 Connection between the modulus of deformation Ev and

the coefficient of ballast .................................................................................. 2849.7.2.1 Determination of the coefficient of ballast from settlement measurements ...... 2849.7.2.2 Determination of the coefficient of ballast from rail tensions ............................ 2849.7.2.3 Determination of the coefficient of ballast from the length of the

bending wave ................................................................................................. 2859.7.2.4 Determination of the ballast bed figure from the subsidence of the sleeper .... 2859.7.3 The spring rate of the permanent way ............................................................ 2859.7.4 Dynamic track stiffness ................................................................................... 2869.7.4.1 The dynamic modulus of elasticity .................................................................. 2879.7.5 The optimal settlement of the sleeper ............................................................. 2889.8 The resistance of the ballasted track to lateral displacement ............... 2909.9 The critical speed of the permanent way ................................................. 2909.9.1 Shearing wave speed for the isotropic half-space .......................................... 2929.10 Reasons for the development of fines ...................................................... 2929.10.1 Fines in cleaned ballast – new ballast ............................................................. 2929.10.2 Fines developing by tamping and traffic load .................................................. 2929.10.3 Fines developing due to sediments from the air ............................................. 2929.10.4 Fines developing during transportation ........................................................... 2939.11 Distribution of fines in the ballast bed ...................................................... 2939.12 In search of an optimum track structure .................................................. 2949.12.1 The JR Central model ..................................................................................... 2949.12.1.1 Explanation of convergence of the required quality level ................................. 2949.12.1.2 Model of the rate of deterioration ................................................................... 2959.12.2 The Delft University model .............................................................................. 2969.12.3 Dynamic track models .................................................................................... 2969.13 How to produce track of highest initial quality ........................................ 2979.14 Ballasted tracks with cross sleepers ........................................................ 2989.15 Ballasted track for high-speed lines ......................................................... 2999.15.1 Required properties for a ballasted track on high-speed lines ........................ 2999.15.2 Further development of the ballasted track ..................................................... 3019.15.2.1 The Frame Sleeper Track ................................................................................ 3029.15.2.2 The Ladder Sleeper ........................................................................................ 3049.15.2.3 The Broad Sleeper ......................................................................................... 3069.15.2.4 The soled sleeper ........................................................................................... 3069.15.2.5 Softer rail pads with broader rails ................................................................... 3069.15.2.6 Sleepers with larger supporting surfaces ........................................................ 3079.15.2.7 Insertion of matting below the ballast ............................................................. 3079.15.2.8 Highly elastic rail fastenings ............................................................................ 308

10 The slab track ........................................................................................... 309

10.1 Requirements of slab track ........................................................................ 309

Contents

18

10.1.1 Non-settling subsoil ........................................................................................ 30910.1.2 Precise construction and strength of the upper bound bearing layers ............ 30910.1.2.1 Concrete bearing layer ................................................................................... 30910.1.2.2 Asphalt bearing layer ...................................................................................... 31010.1.2.3 Hydraulically bonded bearing layer ................................................................. 31010.1.3 Precise construction and strength of the lower unbound bearing layers ......... 31010.1.3.1 Frost protective layer ...................................................................................... 31010.1.3.2 Subsoil ........................................................................................................... 31010.1.3.3 Sound protection requirements ...................................................................... 31110.1.3.4 Transition from slab track to ballasted track .................................................... 31110.1.3.5 Requirements for the signalling systems ......................................................... 31110.1.3.6 Electro-technical requirements ........................................................................ 31110.2 The slab track in tunnels ............................................................................ 31210.3 The slab track on earth structures ............................................................ 31210.4 Comparison between ballasted track / slab track .................................. 31210.4.1 Advantages of slab track ................................................................................ 31310.4.2 Disadvantages of slab track ........................................................................... 31310.5 Economic efficiency and cost of the slab track ...................................... 31510.6 Design types of slab track ......................................................................... 31510.6.1 Inserted design types on support points with sleeper ..................................... 31610.6.1.1 The Rheda design .......................................................................................... 31610.6.1.2 Rheda-Berlin Design ....................................................................................... 31710.6.1.3 Rheda 2000 Design ........................................................................................ 31810.6.1.4 Heitkamp design ............................................................................................ 31810.6.1.5 Züblin Design ................................................................................................. 31810.6.2 Laid-on design ............................................................................................... 32010.6.2.1 SATO design .................................................................................................. 32110.6.2.2 FFYS design ................................................................................................... 32110.6.2.3 ATD design ..................................................................................................... 32210.6.2.4 BTD design .................................................................................................... 32210.6.2.5 GETRAC design ............................................................................................. 32310.6.3 Monolithic designs on supporting points without sleeper ................................ 32310.6.3.1 Lawn track design for long-distance railways ................................................. 32310.6.3.2 FFC design ..................................................................................................... 32410.6.4 Pre-fabricated designs on supporting points without sleeper ......................... 32510.6.4.1 Bögl design .................................................................................................... 32510.6.4.2 ÖBB-Porr design ............................................................................................ 32610.6.4.3 Plate track in Japan ........................................................................................ 32610.6.5 Continuous support with sealed rail ................................................................ 32710.6.5.1 INFUNDO design ............................................................................................ 32710.6.6 Continous support with squeezed rail ............................................................. 32910.6.6.1 SFF design ..................................................................................................... 32910.6.6.2 SAARGUMMI design ...................................................................................... 32910.7 Comparison of overall heights of various designs of slab track ........... 33010.8 Technical and economic comparison of the slab track designs ............ 331

11 Interaction between wheel and rail .................................................... 333

11.1 Dynamics of vehicle movement ................................................................. 33311.1.1 Starting forces ................................................................................................ 333

Contents

19

11.1.2 The starting resistance wa .............................................................................. 33311.1.3 Gradient resistance ws .................................................................................... 33311.1.4 Curvature resistance wk .................................................................................. 33411.1.5 Running resistance wt of vehicles ................................................................... 33511.1.6 Air resistance .................................................................................................. 33511.1.7 Running resistance of trains according to Strahl wv ........................................ 33511.1.8 Acceleration resistance wa .............................................................................. 33511.1.9 Equivalent conicity .......................................................................................... 33611.2 The contact between wheel and rail ......................................................... 33911.2.1 The Hertz surface pressure ............................................................................. 34011.2.2 Contact mechanics ........................................................................................ 34011.2.2.1 Kalker coefficients ........................................................................................... 34011.2.2.2 Frictional connection ...................................................................................... 34111.3 The influence of the rail / wheel contact geometry ................................. 34211.4 Vehicle defects ............................................................................................ 34211.4.1 Noncircular wheels ......................................................................................... 34211.5 Forces acting on the track due to dynamic wheel loads ........................ 34311.5.1 Interaction of the vehicle and defects in track geometry ................................. 34411.5.1.1 Types of vehicle vibration ................................................................................ 34411.5.2 Dynamic vehicle forces occurring through individual defects .......................... 34611.5.2.1 Flats on the wheel .......................................................................................... 34611.5.2.2 Dynamic stress in rail joints ............................................................................ 34611.5.2.3 Dynamic strain in mud joints ........................................................................... 34711.5.3 Vertical sleeper gap when a train passes sleepers in a defective position ....... 34911.5.3.1 Strains by noncircular wheels ......................................................................... 35011.6 Rail vehicle noise ........................................................................................ 35111.6.1 Reason for the sound ..................................................................................... 35111.6.2 Consequences of coarse rail surfaces ............................................................ 35211.6.3 Consequences of coarse wheels .................................................................... 35311.7 Assessment and measurement of vehicle reactions ............................... 35511.7.1 The “SR” method of the DB AG ..................................................................... 35611.7.2 The “VRA” system of the NS .......................................................................... 35611.8 The requirements of the track for the vehicle .......................................... 35611.9 The optimum vehicle ................................................................................... 35611.9.1 The track geometry – a mathematical description as a basis for

vehicle design ................................................................................................. 35711.9.2 Synthesis of a classified track from density spectra of track unevenness ....... 36011.9.3 Analysis of vehicle responses by means of classified tracks ........................... 36011.9.4 Possibilities of improvement of running gears ................................................. 36011.10 Tilting trains ................................................................................................. 36011.10.1 Tilting trains with active control system ........................................................... 36111.10.2 Tilting trains with passive control systems ...................................................... 36111.11 Vehicle monitoring ...................................................................................... 361

12 The switches ............................................................................................. 363

12.1 The tasks of switches, crossings and diamond crossings with slips ... 36312.2 The main types of switches, crossings and diamond crossings

with slips ...................................................................................................... 36312.2.1 Single switches .............................................................................................. 363

Contents

20

12.2.2 Double switches ............................................................................................. 36412.2.3 Crossings and diamond crossings with slips .................................................. 36412.2.4 Curved points ................................................................................................. 36512.2.5 Vertex clothoid switches ................................................................................. 36512.3 Designation of switches ............................................................................. 36512.4 Elements of switches .................................................................................. 36612.4.1 The blade ....................................................................................................... 36612.4.1.1 Design types of blades ................................................................................... 36612.4.1.1.1 Loose heels .................................................................................................... 36612.4.1.1.2 Flexing blades ................................................................................................ 36712.4.1.2 Spring switch blades ...................................................................................... 36712.4.1.3 Flexing blades without switch rail plates ......................................................... 36812.4.2 Switch-blade rolling device ............................................................................. 36812.4.3 Optimisation of the running edge .................................................................... 36912.4.4 The stock rail .................................................................................................. 36912.4.5 The switch diamond ....................................................................................... 37012.4.5.1 Design of built-up common diamonds ............................................................ 37012.4.5.1.1 Cast-steel diamonds ...................................................................................... 37112.4.5.2 Built-up diamonds .......................................................................................... 37112.4.5.3 Built-up rail diamonds ..................................................................................... 37112.4.5.4 Filled section rail diamonds ............................................................................. 37212.4.5.5 Profiled monoblock diamonds ........................................................................ 37212.4.5.6 Diamonds with movable tips .......................................................................... 37312.4.6 The wing rails ................................................................................................. 37312.4.7 The check rail ................................................................................................. 37312.4.8 Switch locks ................................................................................................... 37312.4.9 Hydraulic switch drive ..................................................................................... 37412.4.10 Switch heating ................................................................................................ 37412.4.11 Groove width, dimension for point protection and distance between

guiding surfaces ............................................................................................. 37412.4.12 Switch diagnosis systems .............................................................................. 37412.5 The vibration-damped switch with divided long sleepers ...................... 37612.6 Geometric and structural characteristics of switches ............................ 37712.6.1 The switch radius ........................................................................................... 37712.6.1.1 The lateral acceleration ................................................................................... 37712.6.1.2 The change in lateral acceleration (the jerk) .................................................... 37812.6.1.3 The switch inclination ..................................................................................... 37812.7 Schematic representation of switches ..................................................... 37912.8 Settlement behaviour of switches ............................................................. 37912.9 Maintenance of switches ........................................................................... 37912.9.1 Inspection of sleepers .................................................................................... 37912.9.2 Preparatory works .......................................................................................... 37912.10 Overlaps of rails .......................................................................................... 381

13 Overhead line system ............................................................................. 385

13.1 Types of traction current ............................................................................ 38513.2 Direct current systems (DC) ....................................................................... 38713.3 Alternating current systems (AC) .............................................................. 38713.4 Catenary ....................................................................................................... 387

Contents

21

13.5 Air distances ................................................................................................ 39013.6 Various designs of overhead lines ............................................................. 39013.7 Structure of longitudinal catenary ............................................................. 39213.8 Return of traction current .......................................................................... 39513.9 Admissible contact voltage ........................................................................ 39613.10 Interaction between current collectors and overhead line ..................... 397

14 Fundamentals on guiding and signalling in railway operation .... 39814.1 Block sections ............................................................................................. 39814.2 Track circuits ............................................................................................... 39814.2.1 Insulated rails ................................................................................................. 39814.2.2 Insulating joints ............................................................................................... 39814.3 Axle counters ............................................................................................... 39814.4 Intermittent automatic train control .......................................................... 39914.4.1 Inductive train control ..................................................................................... 40014.5 Continuous train control (CTC) .................................................................. 40014.5.1 Track conductors ........................................................................................... 40014.6 The European rail traffic management system ERTMS .......................... 40014.7 Automatic train stop ................................................................................... 40114.8 Hot box detection ........................................................................................ 401

15 Track maintenance .................................................................................. 402

15.1 Typical maintenance cycles ....................................................................... 40215.2 Standard values for maintenance and danger limits ............................... 40215.2.1 Standard values for maintenance and danger limits concerning the

track position .................................................................................................. 40315.2.2 Standard maintenance values for defects on the rail surface .......................... 40415.2.3 Standard maintenance values – cross profile of the rail head ......................... 40515.3 Accuracy of acceptance ............................................................................. 40515.4 Considerations on the track quality .......................................................... 40615.4.1 Course of track quality ................................................................................... 40615.4.2 Cumulative curve of track defects .................................................................. 41215.5 The choice of the optimum duration of track possessions .................... 41315.6 Correction of track geometry .................................................................... 41415.6.1 Track geometry measurement ........................................................................ 41415.6.1.1 Manual measurement ..................................................................................... 41515.6.1.1.1 Moving-chord measurement ........................................................................... 41515.6.1.1.2 Calculation of the location from symmetric versine values .............................. 41515.6.1.1.2.1 Transfer function ............................................................................................. 41615.6.1.1.3 Requirements of track geometry .................................................................... 41915.6.1.1.4 Recording car requirements ........................................................................... 42015.6.1.1.5 Multifunctional recording cars ......................................................................... 42015.6.1.1.6 Measured parameters and marginal conditions .............................................. 42115.6.1.1.6.1 Track geometry parameters ............................................................................ 42115.6.1.1.6.2 Subsoil parameters ........................................................................................ 42215.6.1.1.6.3 Ballast parameters .......................................................................................... 42215.6.1.1.6.4 Rail measurement ........................................................................................... 42215.6.1.1.6.5 Measurement of the overhead line .................................................................. 42415.6.1.1.6.6 Measurement of the track surroundings and track inspection ......................... 425

Contents

22

15.6.1.1.7 Vehicle dynamics ............................................................................................ 42715.6.1.1.8 The multifunctional recording car UFM160 ...................................................... 42815.6.1.2 Small devices for track geometry measurement ............................................. 42915.6.1.3 3D Recording by helicopters .......................................................................... 42915.6.2 Surveyed track – measurement and calculation of track correction values ..... 43015.6.2.1 Manual fixed-point measurement..................................................................... 43115.6.2.2 Versine and level measurement device ........................................................... 43115.6.2.3 Track surveying car EMSAT ............................................................................ 43115.6.2.3.1 Description of the Fixed-point Measurement Device ....................................... 43315.6.2.3.2 Use of the EMSAT for track and switch renewal ............................................. 43515.6.2.3.3 Measurement evaluation and decision on necessary measures ...................... 43515.6.2.3.4 Transmission and storage of measurement documentation ............................ 43515.6.2.3.5 Combination of EMSAT and GPS ................................................................... 43615.6.2.3.6 The GPS satellite measurement technique for the measurement

of surveyed tracks .......................................................................................... 43615.6.2.3.6.1 Phase measurement error �

�......................................................................... 436

15.6.2.3.7 State of realisation .......................................................................................... 43815.6.2.3.8 Application of the combined EMSAT – GPS system ....................................... 43915.6.2.3.9 The combination of the EMSAT with a Ballast Profile Measurement System .. 44015.6.2.4 The PALAS system ......................................................................................... 44115.6.2.5 Automatic guiding computer WINALC for tamping machines ......................... 44115.6.2.5.1 Functions of the WINALC ............................................................................... 44215.6.2.5.1.1 Entry of target geometry data ......................................................................... 44215.6.2.5.1.2 Electronic versine compensation and track geometry optimisation ................. 44215.6.2.5.1.3 Determination of correction values from versine differences ............................ 44415.6.2.6 Track measuring run and guiding of the tamping Machine

by Combined Level-alignment Laser .............................................................. 44415.6.2.7 Track measuring run and guidance of the tamping machine

by Curve Laser CAL ....................................................................................... 44615.6.2.8 Measurement and machine guiding via complete measuring station .............. 44715.6.2.9 Correction of track geometry – tamping ......................................................... 44815.6.2.9.1 Preparatory track works ................................................................................. 44815.6.2.9.1.1 Preparation of rail fastenings .......................................................................... 44915.6.2.9.1.2 Track gauge correction ................................................................................... 44915.6.2.9.1.3 Treatment by welding ..................................................................................... 44915.6.2.9.1.4 Correction of minor defects ............................................................................ 44915.6.2.9.1.5 Preparation of switches .................................................................................. 44915.6.2.10 The track position correction (track lining, track lifting) .................................... 45015.6.2.10.1 Compensation lining method .......................................................................... 45015.6.2.10.1.1 The electronic versine compensation .............................................................. 45115.6.2.10.1.2 4-Point-lining method ..................................................................................... 45115.6.2.10.2 Precision lining and levelling method .............................................................. 45215.6.2.10.3 Tamping ......................................................................................................... 45415.6.2.10.4 Asynchronous Equal-Pressure Tamping ......................................................... 45415.6.2.10.5 Tamping parameters ....................................................................................... 45515.6.2.10.6 Optimum lifting ............................................................................................... 45815.6.2.10.7 Controlled “Design Overlift”.............................................................................. 45815.6.2.10.8 Plain-line tamping machines ........................................................................... 46015.6.2.10.8.1 Admissible lifting values for tamping machines ............................................... 461

Contents

23

15.6.2.10.8.2 Continuous-action tamping machines ............................................................ 46115.6.2.10.8.3 Equipment of tamping machines .................................................................... 46215.6.2.10.8.4 09-3x Dynamic Tamping Express ................................................................... 46315.6.2.10.8.5 Mechanised elimination of individual defects .................................................. 46515.6.2.10.9 Switch tamping machines .............................................................................. 47115.6.2.10.9.1 Synchronous Three-Rail Lifting and Four-Rail Tamping ................................... 47115.6.2.10.9.2 Proof of the reduced stress on switches by calculation using

the Finite Element Method (FEM) .................................................................... 47515.6.2.10.9.3 Results of the FEM Calculation ....................................................................... 47615.6.2.10.9.4 Practical proof of the effectiveness of 3-Point lifting ........................................ 47715.6.2.10.9.5 Laser controlled 3-Point lifting ........................................................................ 47715.6.2.10.10 Stone blowing ................................................................................................ 47915.6.2.10.11 The Dynamic Track Stabiliser DTS .................................................................. 48215.6.2.10.11.1 Parameters influencing the track stabilisation ................................................. 48215.6.2.10.11.2 The influence of the stabilising frequency ....................................................... 48315.6.2.10.11.3 The influence of vertical static load ................................................................. 48315.6.2.10.11.4 The influence of working speed ...................................................................... 48515.6.2.10.11.5 The influence of the dynamic power of impact ............................................... 48515.6.2.10.11.6 Connection between lifting and settlement by the DTS .................................. 48615.6.2.10.11.7 Connection between settlement and gain in lateral resistance ........................ 48715.6.2.10.11.8 Empiric stabiliser formula ................................................................................ 48815.6.2.10.11.9 Deep action of the DTS .................................................................................. 48815.6.2.10.11.10 Increased resistance to lateral displacement achieved by the DTS ................. 48815.6.2.10.11.11 The continuous dynamic measurement of lateral track resistance .................. 48815.6.2.10.11.12 Longer maintenance cycles achieved by the DTS .......................................... 49015.6.2.10.11.13 Increased track quality reserve by homogenizing with

layer-by-layer stabilisation ............................................................................... 49115.6.2.10.11.14 Increased durability of long-wave defects by the DTS .................................... 49215.6.2.10.11.15 Spatial compaction by the DTS ....................................................................... 49215.6.2.10.11.16 Influence of the DTS on subsoil and vertical elasticity ..................................... 49615.6.2.10.11.17 Reduction of local rail tensions by the DTS .................................................... 49615.6.2.10.11.18 Influence of the DTS on structures ................................................................. 49815.6.2.10.11.19 Measured acceleration of the DTS ................................................................. 49815.6.2.10.11.20 Economic efficiency of the DTS ....................................................................... 50015.6.2.10.12 The sleeper crib consolidator ......................................................................... 50115.6.2.10.13 The shoulder consolidator .............................................................................. 50115.6.2.10.14 Sleeper end consolidator ................................................................................ 50115.7 Correction of rail defects ........................................................................... 50115.7.1 Rail measurement ........................................................................................... 50115.7.1.1 Rail profile measurement ................................................................................ 50115.7.1.1.1 Contact scanning of the rail profile ................................................................. 50115.7.1.1.2 Optic rail profile measurement ........................................................................ 50115.7.1.2 Corrugation measurement .............................................................................. 50215.7.1.2.1 Manual corrugation measurement .................................................................. 50215.7.1.2.2 Inertial corrugation measurement device ........................................................ 50315.7.1.2.3 Corrugation measurement device on versine basis ......................................... 50415.7.1.2.4 Corrugation measurement device based on acceleration measurement ......... 50515.7.2 Correction of rail defects ................................................................................ 50515.7.2.1 Rail grinding ................................................................................................... 506

Contents

24

15.7.2.1.1 Preventive grinding of new rails ...................................................................... 50615.7.2.1.2 Noise grinding ................................................................................................ 50715.7.2.1.3 Special Grinding ............................................................................................. 50915.7.2.1.4 Grinding by rotating grinding stones ............................................................... 50915.7.2.2 Mobile small-scale rail grinding devices .......................................................... 50915.7.2.2.1 Grinding with oscillating stones ...................................................................... 50915.7.2.3 Rail planing ..................................................................................................... 51215.7.2.3.1 Reprofiling of rails by planing .......................................................................... 51415.7.2.4 Rail milling ...................................................................................................... 51515.7.2.5 Rail straightening – STRAIT ............................................................................ 51515.7.2.6 Rail welding .................................................................................................... 51615.7.2.6.1 Thermite welding ............................................................................................ 51615.7.2.6.2 Mobile flash-butt welding ................................................................................ 51715.8 Ballast bed treatment ................................................................................. 52015.8.1 Measurement of the ballast bed profile ........................................................... 52015.8.2 Ballast bed cleaning ....................................................................................... 52115.8.2.1 Longitudinal cutting ........................................................................................ 52315.8.2.1.1 Longitudinal machine guidance via a laser reference plane ............................. 52315.8.2.2 The cross-fall of the track formation ............................................................... 52515.8.2.3 The excavation capacity of the excavation chain ............................................ 52515.8.2.4 Throughput, recovery and screening quality ................................................... 52815.8.2.5 Dependence of the screen performance on the moisture contained in

the excavated material ................................................................................... 53115.8.2.6 Performance of ballast cleaning machines ...................................................... 53215.8.2.7 Screen surface dimension and screen performance ....................................... 53215.8.2.8 Screen charging ............................................................................................. 53415.8.2.9 Screen calculation .......................................................................................... 53415.8.2.10 Ballasting ........................................................................................................ 53615.8.2.11 Excavation Width ............................................................................................ 53715.8.2.12 Excavation depth ............................................................................................ 53815.8.2.13 Modern cleaning machines ............................................................................. 53915.8.2.13.1 Cleaning machines of the RM80 / RM90 Series ............................................. 53915.8.2.13.2 High-performance cleaning machines of the RM800 / RM900 series ............. 54015.8.2.13.2.1 High-performance cleaning machine RM800 ................................................... 54215.8.2.13.2.2 High-performance cleaning machine RM801 ................................................... 54215.8.2.13.2.3 High-performance cleaning machine RM802 ................................................... 54215.8.2.13.2.4 High-performance cleaning machine of the RM900 series .............................. 54315.8.2.13.3 Modern measurement and control systems for high-performance

cleaning machines .......................................................................................... 54415.8.2.13.4 Excavation chain control and lifting control ..................................................... 54415.8.2.14 Lining control on cleaning machines ............................................................... 54515.8.2.14.1 Lining by using the target geometry ............................................................... 54515.8.2.14.2 Lining on the basis of a position image derived from symmetrical

versine values ................................................................................................. 54515.8.3 Vegetation control ........................................................................................... 54615.8.3.1 Spraying trains ............................................................................................... 54615.8.3.2 Thermal infrared control TIC ........................................................................... 54615.8.3.3 Vegetation cutting ........................................................................................... 54615.8.4 Vacuum excavating method ........................................................................... 547

Contents

25

15.8.4.1 Shoulder cleaning machines ........................................................................... 54715.8.5 Ballast distribution and conveying systems ..................................................... 54815.8.5.1 MFS System ................................................................................................... 54815.8.6 Ballast distributing and regulating machines ................................................... 54915.8.6.1 Universal ballast distributing and regulating machines .................................... 55215.8.6.1.1 Universal ballast distributing and regulating machines of the USP series ........ 55215.8.6.1.2 Plain-line ballast regulating and profiling machine, SSP series ........................ 55215.8.7 Ballast Distribution System ............................................................................. 55415.9 Subsoil improvement .................................................................................. 55615.9.1 Measurement of the subsoil conditions .......................................................... 55615.9.1.1 Georadar ........................................................................................................ 55615.9.1.2 Subsoil examination machine ......................................................................... 55615.9.2 Insertion of formation protective layers ........................................................... 55915.9.2.1 Traditional method .......................................................................................... 56015.9.2.2 Insertion of track formation protective layers using ballast cleaning machines 56015.9.2.3 Formation rehabilitation machine SVV100........................................................ 56215.9.2.4 Formation rehabilitation machine PM200-2R .................................................. 56415.9.2.5 Formation rehabilitation machine AHM800R ................................................... 56415.9.2.6 Formation rehabilitation machine RPM2002..................................................... 56615.9.3 Methods of soil upgrading .............................................................................. 56615.9.3.1 Traditional methods ........................................................................................ 56715.9.3.1.1 Improvement by adding cement according to the

cutting-mixing-injection method ...................................................................... 56715.9.3.1.2 Soil replacement ............................................................................................. 56715.9.3.1.2.1 Box-soil replacement method ......................................................................... 56715.9.3.1.2.2 Moving pre-structure with integrated soil upgrading unit (WARAN) ................. 56715.9.3.2 Soil and formation upgrading according to the PUSCAL method ................... 56715.9.3.3 Formation upgrading machine PM150FS ....................................................... 56715.10 Laying and relaying of the track grid ........................................................ 56815.10.1 Historical outline ............................................................................................. 56815.10.2 The track relaying train ................................................................................... 57015.10.2.1 Preparatory work ............................................................................................ 57215.10.2.2 Track relaying train SUZ500UVR ..................................................................... 57215.10.3 Rail pulling and pushing device ...................................................................... 57215.11 Laying and transportation of switches ..................................................... 57415.11.1 Plug-in switches ............................................................................................. 57415.11.2 Switch transporting wagon, WTW series ........................................................ 57415.11.3 Switch relaying machine, WM series .............................................................. 57515.11.4 Switch relaying by cranes ............................................................................... 57515.11.5 Switch relaying with the UWG ........................................................................ 57615.12 Track construction cranes ......................................................................... 57615.13 Maintenance of overhead lines .................................................................. 57715.13.1 Disassembly of existing catenary .................................................................... 57715.13.1.1 Motor Platform Wagon MGW ......................................................................... 57815.13.1.2 Motor Tower Wagon MTW ............................................................................. 57915.13.1.3 Overhead Line Drum Wagon FWW ................................................................. 58015.13.1.4 Mast Erecting Device MAGE75........................................................................ 58015.13.2 Assembly of new catenary .............................................................................. 58115.13.2.1 Overhead Line Relaying Machine FUM ........................................................... 582

Contents

26

15.13.2.2 Assembly Car A10........................................................................................... 58315.13.3 Assembly of the line feeder and the return line ............................................... 583

16 Life cycle costs of railways ................................................................... 585

16.1 UIC-study comparing the LCC of railways ............................................... 58516.1.1 Results of the LCC cost comparison for railways ........................................... 58516.2 Factors forcing up costs ............................................................................ 58716.3 Cost saving potentials ................................................................................ 58816.4 Differential LCC ........................................................................................... 58916.4.1 Net present value method and internal rate of interest .................................... 58916.4.2 Standard kilometers ....................................................................................... 59016.4.3 Composition of the annual costs .................................................................... 59016.4.4 Results of the differential LCC calculation ....................................................... 59116.4.4.1 Speed restrictions at the end of the lifetime .................................................... 59116.4.4.2 Maintenance strategies for lines on poor substructures .................................. 59116.4.4.3 Heavy or innovative permanent way ............................................................... 59216.4.4.4 Combination of tamping and grinding ............................................................. 59216.4.4.5 Maintenance cycles increased by dynamic track stabilisation ......................... 59416.5 Track maintenance costs ........................................................................... 59416.6 The effect of mechanisation on the economic efficiency

of permanent-way maintenance ................................................................ 59416.7 Track access charges ................................................................................. 595

Literature .................................................................................................... 597

Keywords ................................................................................................... 624

Advertisers’ Index .................................................................................... 634

Contents

27

1 General information

28

1 General information

This track manual is intended to make clear that the track consists not only of individual componentsviewed separately, but the “railway wheel-track” system as a whole.

The track must:• guide vehicles without risk of derailment,• take up vertical and horizontal vehicle forces,• off-load these forces via the track grid and ballast bed into the subsoil,• ensure high passenger comfort and• high availability for train traffic

The railway wheel transmits vertical and horizontal forces onto the track. Furthermore, the long weld-ed railway track is subject to the influence of longitudinal forces arising because of changes in tem-perature. The track is stressed by quasi-static (low-frequency) and dynamic force components ofhigher frequency. Figure 1 schematically represents the Wheel-Track system.

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Figure 1: Schematic representation of the Wheel-Track system

The individual parts of this system are linked by components exerting elastic and damping effects.The elastic and damping elements between vehicle body and bogie, as well as between bogie andwheelset, are very well known and their behaviour can be very well expressed mathematically.

The track itself with its elasto-plastic properties cannot be expressed by an exact analysis becauseof the inhomogeneous behaviour of the ballast bed, the protective layer of the formation and the sub-soil. Empiric parameters and connections found out by experiments are used for this purpose.

The strength of these forces is a function of the axle load, of changes in wheel loads when drivingon curves or in case of unequal loading, of braking and starting, and the rolling of ovalized unbal-anced wheels on a defective track.

The track grid has to distribute these forces in such a way, that the maximum admissible values forballast compression below the sleeper and the admissible compressive strain on the soil will not beexceeded.

Figure 2 shows the increase of wheelset loads and speeds in the course of railway history. It isremarkable how the wheelset loads for goods wagons have steadily risen to today’s value of 22.5tons – in the future it will be 25 tons. The speed of passenger trains has also increased: 250 to 300km/h on new tracks. Trains in general run at a higher speed nowadays, even on the rest of the rail-way network.

1 General information

30

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Figure 2: Chronological development of wheelset loads and train speeds, for passengerand goods trains [1]

The theoretical comments and practical experience stated in the following are intended to explainhow to fulfil these higher requirements which, undoubtedly, will rise even further in the future.

Permanent way for high-density lines, which, according to modern knowledge, requires only a littlemaintenance, consists of the following elements:• heavy-profile rail UIC60,• hard-wearing rails in curves (head-hardened or high-alloy),• concrete sleepers of optimized quality for track and switches (soled sleepers, broad sleepers,

frame sleepers, ladder sleeper track, etc.),• torsion-resistant and elastic rail fastenings (optimization of elasticity and damping is necessary),• permanently stable ballast bed and• permanently stable, frost resistant track formation (by the insertion of protective layers and geo-

textiles).

1 General information

31

6 Ballast and ballast bed

The track grid is carried in the track bed on a “floating” support. This causes the track geometry todeteriorate under the influence of dynamic forces, however, it has the advantage that this deteriora-tion may be remedied at low cost by fully automated permanent-way machines.

6.1 Ballast bed requirements

The ballast bed has to provide the following functions:• to transmit the sleeper pressure to the subsoil as evenly as possible,• to have high resistance to longitudinal and lateral sleeper displacement,• to easily re-establish the track position after it has been changed (tamping and lining),• to have good air and water permeability to maintain the bearing capacity of the subsoil,• to ensure the track elasticity in order to minimize dynamic forces, and• to enable corrective actions in the track (tamping and lining).

These requirements may be met in the following ways through:• choice of the ballast bed thickness,• choice of the ballast bed cross section,• choice of the ballast quality, and• quality of ballast consolidation.

The following factors may have an adverse influence on these properties:• operational load: due to the wheels rolling over the track the sleeper is lifted off and rebounds on

the ballast, the dynamic forces may overstress the ballast and lead to shelling, grain shifting andabrasion,

• maintenance work – wear by tamping or cleaning,• material rising from the subsoil, if there are no formation protection layers or if they are defective,

and• ballast contamination by lost cargo (coal, ore, sand, etc.), remainders of vegetation and other envi-ronmental influences (frost, fluctuation of temperature, moisture, etc.).

6.1.1 The ballast bed cross-section

The ballast thickness – this is the distance between the lower surface of the sleeper and the subsoil– should be as large as possible ([189], [190]). The pressure distribution lines should intersect, oth-erwise the subsoil would be pressed up between the sleepers.• The required ballast bed thickness depends on:• the sleeper spacing,• the sleeper width, and• the angle of friction of the ballast.

The thickness of the ballast bed should be at least 30 cm for axle loads of 220 kN, a sleeper spac-ing of 60cm and a sleeper width of 28 cm. For high-speed lines a thickness of 40 cm is advisable.

It is important to provide 45 to 50 cm of ballast at the sleeper ends. This guarantees a significantresistance to lateral displacement.

6.1 Ballast bed requirements

189

The ballast bed cross section should have the following target dimensions:

ballast width at the sleeper ends:• 0.4 m at v 160 km/h,• 0.5 m at v > 160 km/h, and• 0.45 m for B75 sleepers (sleeper length: 2.8 m), and• ballasting up to the upper edge of the sleeper.

Inclination of the ballast shoulder:• 1:1.5 designed,• 1:1.25 implemented, and• a cross fall of the formation of 1:20

Minimum ballast bed thickness below the lower sleeper edge (measured below the low rail)• 0.3 m for existing lines, and• 0.35 m or 0.40 m, respectively, for new lines.

This means that the thickness of the ballast bed increases adequately below the superelevated rail,furthermore, the formation has to be broadened correspondingly.

It is advisable to provide ballast of high compactness and tension. This can be reached by insertingand compacting the ballast in layers. The best way to insert the ballast in layers is with the help of atamping machine, sleeper end consolidators and a dynamic track stabiliser.

6.1.2 Ballast materials

The raw material for permanent-way ballast has to meet the following requirements [191]:• resistance to weather influences (to be determined by the freeze-thaw test),• high toughness (determined in the rotary drum grinder),• high resistance to pressure (determined by pressure and impact tests),• no loam or earth content, and• the rocks should break into sharp-edged cubes.

The most suitable materials are hard ballast (basalt, diabase, granite) which meet the above require-ments. Soft rocks (limestone, dolomite, sedimentary rocks) are usually less suitable.

6.1.2.1 Crushed ballast

The following ballast parameters should correspond to the intended purpose:• grain size and grain size distribution according to the screen analysis,• grain shape (cubic, sheet-shaped, oblong),• undersize and oversize (5% is usually tolerated).

It is common practice to use crushed ballast of 25–60 mm for main-line tracks and of 15–30 mm forsecondary tracks. The use of smaller ballast sizes in shunting tracks helps to avoid accidents [192].

The granulometric properties of the ballast grains should be the following:• grain size 22.4 / 63 mm with grain size distribution according to figure 97, where the undersize part

< 22.4 mm must not exceed 3% when samples are taken in the factory and 5% when sampledon site,

• at the moment of delivery the ballast has to be clean and free from organic substances.

6 Ballast and ballast bed

190

6.1.2.1.1 Grain shapes

The ballast bed mainly consists of skeleton grain, and, depending on the service life and permanent-way conditions, of distance and filler grain.

Grain size as well as grain shape changes, as material shells and is rubbed off under operationalloads. A new ballast bed consists almost entirely of skeleton grain. Larger particles come off underload, until the contact surfaces are numerous enough to divert the required loads via the ballast. Thedeveloping distance grain improves the resistance to shearing (a distance grain percentage of up to15%, size 15–30 mm, would be the optimum). The percentage of the distance grain, however,increases in the course of time, and additionally finer material, the filler grain, develops, which beginsto enclose the skeleton grain. That is why the angle of internal friction of the material diminishes andits resistance to shearing and bearing capacity is reduced. If the shearing strain becomes too high,a soil fracture might occur.

6.1.2.2 Round ballast

Round ballast (gravel), partly crushed, is used in countries with poor rock deposits. It is not indent-ed and therefore gives only low resistance to lateral displacement; furthermore, major grainrearrangements often occur in this kind of ballast, therefore, settlement values are higher than intracks with crushed ballast. The resistance to shearing of round ballast approximately correspondsto the value of contaminated standard ballast.

6.1 Ballast bed requirements

191

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Figure 97: Admissible range of grain size analysis for new ballast

6.1.2.3 Ballast in bags

Experiments, where fine gravel was filled into plastic bags (the so-called bag permanent-way) andcompressed, have shown that the settlement of these fillings (particularly of fine material of a size of5–7 mm) was comparatively high [193]. Furthermore it is difficult to correct the track position. There-fore, further experiments were abandoned.

6.1.3 Testing of track ballast

For economical reasons railways usually buy their ballast directly from quarries producing road bal-last. Therefore, they usually acknowledge the existing experience and test methods and only slight-ly change the grain size of the ballast.

Major railways have their own test specifications and have the tests carried out by material testingbodies.

6.1.3.1 Los Angeles-test (LA)

This test serves to determine the breaking strength of natural stone. A specimen of about 10 kg in acylinder, together with several steel balls, is revolved 1000 times around its axis at a speed of 33 rpm[194]. After the test the specimen is screened on a 1.6 mm screen. The Los-Angeles value is deter-mined according to the following formula:

mLA = –– · 100 [%]

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m ... weight of the screened fractionM ... specimen weight

6 Ballast and ballast bed

192

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Figure 98: Schematic representation of skeleton grain, distance grain and filler grain