Tracking for High-Speed Trains in India - ?· 7.4 Tracking for High-Speed Trains in India Tilting Train…

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<ul><li><p>J. S. MundreyFormer</p><p>Additional Member (Civil Engineering)Railway Board, Ministry of Railways.</p><p>Prologue</p><p>RITES Journal 7.1 January 2010</p><p>Tracking for High-Speed Trains in India</p><p>Concept of High-Speed Train</p><p>The council of the European Union in their directive no. 96/48/EC has definedthe term High Speed covering all railway express services operated at speeds in the200 to 300 km/h range. This includes railway lines:</p><p>i) Built specially for high speed generally equal to or greater than 250km/h.</p><p>ii) Specially upgraded for high speed travels of the order of 200 km/h.</p><p>The provision of a High Speed service is not restricted to reducing journeytimes. Its undoubted success is also due to the quality associated with High Speedtravel, viz:</p><p> The frequency of service, Regular-interval timetables,</p><p>Indian Railways have drawn up ambitiousplans for developing high speed trainsystems in India. The Author, who is anexpert in track structure and bridges, hasbrought out the different track structuresneeded for operation of high speed trains.</p><p>Various types of tracks, both ballastedand ballast-less track structures, havebeen covered.</p><p>A very informative Article indeed.- Editor</p></li><li><p>7.2 Tracking for High-Speed Trains in India</p><p> A high level of comfort, A pricing structure adapted to the needs of customers, Complementarity with other forms of transport, More on-board and station services.</p><p>A High Speed system is designed to incorporate the whole range of serviceswhich the customer has come to expect when traveling on High Speed trains, includingboth pre-travel services (information, ticket purchasing, seat reservations, etc.) andpost-travel ones (after-sales service).</p><p>High-speed railways, in addition to providing a high level of mobility of people,are greatly advantageous as an environmentally friendly means of transport.</p><p>Transport is responsible for 25% of the worlds carbon dioxide (CO2)emissions, with 80 to 90% coming from cars and highway trucks, and only 2% fromrail. Moreover, emission levels are increasing faster than technological progress dueto the total dependence of road and air transport on oil, and the continuing growth oftraffic. On High-Speed railways the energy consumption per passenger-kilometer isthree and half times less than for a bus, five times less than for air and ten times lessthan that for a private car.</p><p>The social cost of noise, dust, carbon dioxide, nitric oxide and sulfur oxideemission for high-speed rail is one fourth of road transport and one-sixth for air. Itrequires the construction of an eight-lane highway to provide the same capacity as adouble track high-speed railway line.</p><p>Table 1 gives a list of some of the high-speed lines operating at a maximumspeed of 200 Km/h and above with a start-to-stop average speed exceeding 150Km/h.</p><p>Table 1 : Start-to-stop Runs Exceeding 150 Km/h</p><p>Country &amp; Train From To Distance AverageSpeed limit km speedin km/h km/h</p><p>France 320 TGV Lorraine Champagne- 167.6 271.8mph TGV ArdenneJapan 300 Nozomi Hiroshima Kokura 192.0 256.0Belgium 300 Thalys Brussels Valence 831.7 236.5</p><p>Midi TGVGermany 300 ICE Frankfurt Siegburg/ 143.3 226.3</p><p>Flughafen BonnSpain 300 AVE Madrid Zaragoza 307.2 236.3</p><p>Atocha Delicias</p><p>Table contd.</p></li><li><p>J. S. Mundrey 7.3</p><p>Sweden 200 X2000 Skovde Sodertalje Syd 277.0 173.1South Korea 300 KTX Seoul Main Daejeon 160.0 200.0UK 300 Class 395 Ebbsfleet Ashford 53.8 179.3</p><p>International InternationalItaly 250 Eurostar Roma Firenze SMN 261.1 168.4</p><p>TerminiUSA 240 Acela Baltimore Wilmington 110.1 161.1</p><p>Express PennFinland 200 Pendolinos Tikkurila Tampere 177.0 151.7China 200 High speed Beijing Tianjin 118.0 236.0</p><p>C classTaiwan 300 Train 598 Chiayi Taichung 85.9 245.4Austria 200 Railjet St.Polten Linz Hbf 122.7 153.4</p><p>Hbf</p><p>Technologies for High-Speed Operations</p><p>The following two distinct technologies have been adopted for high-speedoperation; these are:</p><p>i) Improvement of the conventional railway operational system.ii) Construction of dedicated High-Speed corridors.</p><p>Improvement of the conventional Railway Operational System : Inadopting this technology the hindrances existing in the operation of high-speed areremoved to the extent possible. These hindrances are in the form of :</p><p>a. Tight horizontal curves The centrifugal forces generated on the curves,vary with the square of the speed. The curves are therefore required to beeased out to keep the centrifugal forces within a manageable limit.</p><p>b. Vertical Curves The desirable values of radii of vertical curves for high-speed operation are much higher.</p><p>c. Level crossing/Grade Separations For high-speed operation, all levelcrossings are required to be replaced by suitable grade separation works.</p><p>d. Fencing On high-speed lines trespassing on tracks cannot be permitted.Thus the entire high-speed line has to be fenced.</p><p>e. Track Geometry:- Very close tolerances in track geometry are requiredto be maintained requiring sturdy track layouts and sophisticated trackmaintenance and monitoring system.</p><p>The problem in respect to tight curves has, to some extent, been solved byadopting tilting train technology.</p></li><li><p>7.4 Tracking for High-Speed Trains in India</p><p>Tilting Train Technology</p><p>All along, since the advent of the railway transportation system, the maximumpermissible speed on the railway lines has been governed by the cant (super elevation)and cant deficiency values. The development of bogie tilting technology, in whichvehicles are tilted depending upon the degree of curvature, has opened a new era ofhigh-speed operation. The tilting of the bogies is achieved by utilizing hydraulic orpneumatic power, while lately electric power is also being utilized. (Fig. 1)</p><p>What tilt achieves</p><p>Tilting trains exploit the fact that speed through curves is principally limitedby passenger comfort, and not by either lateral forces on the track or the risk ofoverturning. The principles and basic equations related to tilting are well known.</p><p>Two primary decisions need to be made. The first is the maximum tilt angleto be provided (tilt); this is based upon the mechanical design of the vehicle. Thesecond decision is what cant deficiency the passengers should experience on aconstant radius curve (CD tilt), which is of primary importance to comfort.</p><p>Given these two decisions, and the value of cant deficiency that applies forthe non-tilting case (CD non-tilt), it is possible to derive an equation for the increasein curving speed, or speed-up, offered by tilt:</p><p> Vtilt sin (cant + tilt + CD tilt ) = </p><p>Vnon-tilt sin (cant + CD non-tilt)</p><p>Maximum track cant is usually 6, and typically 6 of cant deficiency isspecified for a non-tilting train. Applying 9 of tilt and with a cant deficiency of 6 forthe tilting train, the calculation indicates a speed-up of 32%.</p><p>In the light of the above facts tilting trains speed up the trains by about 30%.It is however important to design the transition curves properly, so as to ensure thecomfort level to be within the acceptable limit.</p><p>Dedicated High-Speed Corridors and their Construction Parameters</p><p>For High-Speed operation exclusive corridors have been designed andconstructed. On these corridors construction parameters have been appropriatelyselected for smooth, efficient and safe operation at the designated speed. Theconstruction parameters, which need special attention on these corridors, are:</p><p>a. Horizontal Curves: their radius, cant, cant-deficiency etc. easiestpossible curves are provided on high-speed corridors.</p></li><li><p>J. S. Mundrey 7.5</p><p>b. Ruling Gradient : As the High-Speed trains are lighter in load and areprovided with high tractive power, steeper gradients can be allowed onhigh-speed lines.</p><p>c. Vertical curves : For better passenger comfort, gentler vertical curvesare provided on high-speed lines as compared to that adopted onconventional lines.</p><p>d. Spacing of tracks : On high-speed tracks, provision of wider center-to-center spacing for double lines is important in view of the higher airpressure generated during the crossing of the trains.</p><p>e. Track Structure : Both ballasted and ballast-less track structures havebeen adopted on high-speed lines. The first, high-speed line, New Toikadoline (Tokyo to Osaka) has ballasted track construction. High-speed linesin France and Spain have generally adopted ballasted track construction.Germany and South Korea have also adopted ballasted track structureon some of their high-speed lines. There is however a positive trendtowards the adoption of ballast-less track for high-speed lines.</p><p>The merits and demerits of the two types of track structures have beendiscussed in the succeeding paragraphs.</p><p>Ballasted Track Structure for High Speed (Fig. 2)</p><p>Ballasted track structure is a simple structure consisting of rails, sleepers,rail-to-sleeper fastening system and ballast. Well-compacted subgrade and an efficientdrainage system helps in the maintenance of ballasted track structure to closergeometrical tolerances, an essential requirement for high-speed operation.</p><p>Main Characteristics of Ballasted Track</p><p>In ballasted track, impact forces generated by the oncoming loads aredissipated by the elastic deformation of ballast and the formation underneath,approximately 50% by each of them. In this process, there is also permanent settlementof ballast and formation. In course of time, the ballast gets pulverized/contaminated,loosing its elastic property. Periodical building and recuperation of ballast is requiredfor the ballast to function effectively. Deep screening of ballast is carried out whenfiner particles in the ballast increase the specified limit. The advantages anddisadvantages of adoption of ballasted track for high-speed operation are as under:</p><p>Advantages of ballasted track over ballast-less track are:</p><p>(i) Known and proven method, up to a speed of 350 Kmph.(ii) Low construction cost.</p></li><li><p>7.6 Tracking for High-Speed Trains in India</p><p>(iii) Availability of highly mechanized construction technology.(iv) Good elasticity for efficient absorption of noise and vibrations.(v) Reasonably good maintainability with track machines.(vi) Less sensitive to construction defects.</p><p>Disadvantages of ballasted track when compared to ballast-less track are:</p><p>(i) Track tends to move both vertically and laterally- requires frequent tamping.(ii) Limited uncompensated lateral acceleration possible due to limited lateral</p><p>ballast resistance.(iii) At speeds of 275 Kmph and above, ballast churns up damaging both rail</p><p>and wheels.(iv) Elasticity gets affected with pulverization and contamination; periodic</p><p>deep screening required.</p><p>Main Characteristics of Ballast-less Track</p><p>Ballast-less track rests on solid foundation with no or very little settlement.The elastomeric pads replace the ballast. No maintenance is required except periodicalreplacement of elastic components after their life span is over. There is considerablescope for the reduction of cost of construction of track structure when laid in tunnelsor on viaducts.</p><p>Some of the advantages of ballast-less track are:</p><p>(i) High operational availability- time required for maintenance is almost nil.</p><p>(ii) Long lasting good track geometry.</p><p>(iii) Long life of track structure, 40 to 50 years.</p><p>(iv) Predictable behavior of track components and thus of track geometry.</p><p>(v) High resistance to lateral and longitudinal forces permitting steepergrade and higher speed.</p><p>(vi) Regularity of the rheological (transmission of electric current)properties.</p><p>(vii) Quiet vehicle running, even at high speed.</p><p>Ballast-less tracks however suffers from the following drawbacks:</p><p>(i) Comparatively higher construction cost, particularly when laid on earthformation.</p><p>(ii) Highly sensitive to construction defects.</p><p>(iii) Mechanization of track construction and renewals still in infant stage.</p></li><li><p>J. S. Mundrey 7.7</p><p>Design Philosophy of Ballast-less Track</p><p>Ballast-less track assemblies are expected to provide the same degree ofelasticity in all directions as is available in ballasted track. This is necessary tocontain the static and dynamic forces within acceptable limits. Ballast-less trackassemblies are also expected to perform the following two important functions.</p><p>(i) Dampen the high frequency vibrations of the rail. For that purpose, allballast-less track assemblies have an elastomeric rail pad under the railseat, on which the rail is expected to be under compression at all times.This is similar to the arrangement with the concrete sleepers in ballastedtrack.</p><p>(ii) A medium to distribute the oncoming loads and absorb the energygenerated, functions which are performed by the ballast in the ballastedtrack. This function is performed by incorporating an additional,comparatively softer elastomeric pad in the assembly.</p><p>The above-mentioned basic requirements of the ballast-less track can bemet with by simple assemblies shown in Fig. 3, 4 &amp; 5.</p><p>Further developments in the ballast-less track technology have been promptedby the following considerations:</p><p>a) Construction of track with close tolerances It has to be noted thatballast-less track requires great precision during construction, as anychange in level or alignment is difficult to be carried out at a later stage.</p><p>b) Mechanization of construction In developed countries, labour costsbeing very high, systems have been developed to mechanize the trackconstruction to the extent possible. Pre-fabrication of track componentis one way of reducing labour costs and for increasing the speed ofconstruction</p><p>These technologies have been discussed in subsequent paragraphs.</p><p>Construction parameters as adopted on exclusive High-Speed Corridors</p><p>The geometric parameters as adopted by various world railways on theirhigh-speed corridors are as follows:</p><p>(i) Curves, Horizontals and Vertical</p><p>Horizontal curves are in the range of 7000m to 10000m. For standard gaugetrack, radius and other curve parameters as adopted in various countries are given inTable 2.</p></li><li><p>7.8 Tracking for High-Speed Trains in India</p><p>Table 2 : Curve Parameters</p><p> Country</p><p>Parameters France Germany Spain Korea Japan</p><p>Speeds km/h 300/350 300 350 300/350 350Radius of HorizontalCurves (m) 10 000 7 000 7000 7000 4000Maximum cantin (mm) 180 170 150 130 180Cant deficiency 85 150 100 65 50Maximum grade(mm/m) 35 40 12.5 25 15Cant gradient(mm/s) 50 34.7 32 NA NAMinimum verticalradius (m) 16 000 14 000 24 000 NA 10 000</p><p> (NA = Not Available)</p><p>Spacing of Tracks</p><p>Minimum distance between tracks centers adopted by some of the high-speed networks using standard gauge are given in Table 3.</p><p>Table 3 : Minimum Distance Between Tracks</p><p>Country Minimum distance between tracks (m)at the following speed</p><p> 300 Km/h 350 Km/hFrance 4.2 4.5Germany 4.5 4.5Italy 5.0 5.0Spain 4.3 4.7Japan 4.3 4.3</p><p>Indian Railways provide a centre to centre spacing of 5.35 m between trackson broad gauge for new construction projects, which is sufficient for a high-speedcorridor.</p><p>Ballast-Less Track Technologies of High-Speed Railway Lines</p><p>The following types of ballast-less tracks have been adopted by various worldrailway syst...</p></li></ul>