Track Alignment (The Basics)
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Track Alignment (The Basics) 1 Introduction TOM WILSON FPWI Track Alignment Designers examine the existing track geometry, perform Technical Discipline Leader (Track) alignment calculations and propose alignment solutions which will allow WSP UK trains to safely travel at speed between A and B. For passenger train routes, the effects of travelling along the track (and PWI Vice President for Scotland) horizontal and vertical alignments at speed are an essential part of the Track Designer’s considerations. I’m a professional Permanent Way Engineer have previous experience in providing The aim of this presentation is to provide you with a brief history of the - with more than 46 years’ experience in independent opinion and Expert Witness origins of railway track and introduce you to the basic techniques used to the Rail Industry including working on rail services for solicitors, loss adjusters and rail create modern track alignments. infrastructure projects in the UK, the infrastructure owners. middle East and in Australia. I’ll discuss things like: To do my job, I need to have an up-to-date As an experienced Track Designer and knowledge of current legislation and • How railway tracks were developed from simple wagon ways to Design Manager, I’ve been responsible for industry standards covering all aspects of modern trackforms. production of track designs on a number of track design, installation, maintenance, • The types of geometry elements used in track alignment - and how large UK projects and I’ve led multi- renewal, quality assurance and asset these are connected. disciplinary design teams in the Rail sector condition assessment. • How to use perform simple alignment calculations. in Australia. • The need for design limits to provide safe and comfortable track I’m currently the Technical Discipline systems. Leader for Track in the UK and I have 36 • How to use the design limits and alignment geometry to calculate the track engineers in my UK team with safe speed limits for trains. another 4 in our office in Bangalore. I’ve held posts as Contractor’s Responsible Engineer, Independent Verifier and Design Checker. I’m an A1 Trained Assessor and I 2 A BRIEF HISTORY OF TRACK T R A C K F O R M Track TRACK FUNCTION Alignment (The Basics) TRACK DESIGN (BASICS) DESIGN WORKSHOP 3 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP A (Very) Brief History of Track 4 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Where did it come from? • Heavy wagons with rigid tyres - road surfaces became damaged and rutted • Wagon-ways were developed using stone slabs or wooden baulks to guide wheels 5 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Where did it come from? • Heavy wagons with rigid tyres - road surfaces became damaged and rutted • Wagon-ways were developed using stone slabs or wooden baulks to guide wheels • Guide spacing largely determined by wagon width • Timber replaced with metal by 1793 6 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Where did it come from? CONING OF WHEEL TREADS • Heavy wagons with rigid tyres - road surfaces became damaged and rutted FLANGES • Wagon-ways were developed using stone slabs or wooden baulks to guide wheels AXLE • Guide spacing largely determined by wagon width • Timber replaced with metal by 1793 WHEEL CENTRALLY • Trains are guided by the shape of wheels and the rails. PLACED ON RAIL RAILS SLEEPER STRAIGHT TRACK 7 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Where did it come from? • First passenger railway in 1807 – with horse-drawn carriages… • But the “Permanent Way” had finally arrived! • Heavy steam engines needed stronger rails – wrought iron replaced cast iron in 1820 8 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Where did it come from? • First passenger railway in 1807 – with horse-drawn carriages… • But the “Permanent Way” had finally arrived! • Heavy steam engines needed stronger rails – wrought iron replaced cast iron in 1820 • Track width (rail gauge) a problem until standardised in 1845 • Narrow and Broad gauge railways still exist – and co- exist with Standard Gauge 9 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP TRACK FORM 10 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • Early railways had “T” shaped rails supported on stone blocks • Increasing loads needed stronger rails; breaks were common • Stone blocks were replaced by timbers (cheaper and able to hold track gauge) • Rails with deeper sections between the supports were tried (“fish-belly” rails). • Stone ballast allowed good drainage and enabled realignment… 11 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • … and little has changed; we still install timber track with metal rails on a ballast support layer • Rails are now steel; breaks are uncommon 12 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • … and little has changed; we still install timber track with metal rails on a ballast support layer • Rails are now steel; breaks are uncommon • Highest speed lines tend to use concrete sleepers; but these are not very eco-friendly • Steel sleepers are a more sustainable option – but these require different installation techniques 13 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • … and little has changed; we still install timber track with metal rails on a ballast support layer • Rails are now steel; breaks are uncommon • Highest speed lines tend to use concrete sleepers; but these are not very eco-friendly • Steel sleepers are a more sustainable option – but these require different installation techniques 14 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • Concrete slab track is preferred in tunnels - and on the highest speed lines • Slab track is expensive to install – but it provides good track alignment control 15 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • Concrete slab track is preferred in tunnels - and on the highest speed lines • Slab track is expensive to install - but it provides good track alignment control • Modular pre-cast units allow minor alignment adjustment 16 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What is it made from? • Concrete slab track is preferred in tunnels - and on the highest speed lines • Slab track is expensive to install - but it provides good track alignment control • Modular pre-cast units allow minor alignment adjustment • Transitions to ballasted track are challenging – support stiffness needs to be uniform 17 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP TRACK FUNCTION M O D U L E 1 : TRACK ALIGNMENT GLOBAL ACADEMY FOR RAIL & TRANSIT 18 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What does it do? • Fulfils a service need between A and B 19 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What does it do? Q= 125kN Surface Pressure on Track Formation 2 2 • Fulfils a service need between A and B Ap = 3 cm ; p = 41667 N/ cm 2 2 Ap = 200 cm ; p = 625 N/ cm • Safely guides rail vehicles 2 2 Ap = 510 cm ; p = 245 N/ cm • Transfers loads evenly down to the subgrade 2 2 Ap = 2380 cm ; p = 53 N/ cm (formation) 2 2 Ap = 10100 cm ; p = 12 N/ cm LOAD LOAD SLEEPER PLATES / PADS & FASTENING SLEEPER BALLAST CAPPING LAYER (Sub-Ballast) FORMATION (Subgrade) 20 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What does it do? LOAD LOAD SLEEPER PLATES / PADS & FASTENING SLEEPER • Fulfils a service need between A and B BALLAST • Safely guides rail vehicles CAPPING LAYER (Sub-Ballast) • Transfers loads evenly down to the subgrade FORMATION (Subgrade) (formation) 5000 46 17 2 kg/cm2 kg/cm2 kg/cm2 kg/cm2 WHEEL RAIL SLEEPER BALLAST LOAD BEARING PYRAMIDS OF BALLAST FORMATION LAYERS 21 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What does it do? • Fulfils a service need between A and B • Safely guides rail vehicles • Transfers loads evenly down to the subgrade (formation) • Enables drainage and avoids flooding • Resilient; permanent deformation is resisted 22 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP What does it do? • Fulfils a service need between A and B • Safely guides rail vehicles • Transfers loads evenly down to the subgrade (formation) • Enables drainage and avoids flooding • Resilient; permanent deformation resisted • Allows replacement of worn or defective components 23 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP TRACK DESIGN 24 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP How do we create Track Designs? 2 • Track design combines 3 geometric elements v 1 3 • Curves, spirals and straights C • Curves with a single radius are “Simple”; those with more than one radius are “Compound” Curve Radius Formula 퐂ퟐ R 퐑 = ( ൗퟖ퐯 ) m (Note: All units must be the same) Where: • R is the radius of the curve • C is the length of the chord between two points (i.e. from point 1 to point 3 in the diagram) • v is the offset measured at mid-chord (i.e. at point 2) 25 A BRIEF HISTORY TRACK TRACK TRACK DESIGN OF TRACK FORM FUNCTION DESIGN WORKSHOP Geometry – Curves 2 • Track design combines 3 geometric elements v 1 3 • Curves, spirals and straights C • Curves with a single radius are “Simple”; those with more than one radius are “Compound” • Simple tools can be used to measure curve radius.