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HIGH-SPEED RAILWAY TRACKAlthough alternative track designs, such
as paved track, havebeen developed, the majority of high-speed
railway lines todayfeatures ballasted track. Over the past years,
the laying andmaintenance methods for ballasted high-speed railway
trackhave been optimised, making ballasted track a very
economicalsolution with regard to life-cycle costs. The track of
high-speedrailway lines requires a precise geometry, allowing only
verytight tolerances that must be kept in the millimetre range,
andmust be serviced accordingly from the outset. Neglect of
main-tenance in the initial phase of the service life of high-speed
rail-way track will cause inherent faults that cannot be
compensatedlater.
Interaction between track and rolling stockTrack faults of
different wavelengths stimulate railway vehiclebodies with
different frequencies. Frequencies in the range ofbetween 0.5 and
10 Hz are regarded as critical for rolling stock.At lower speeds,
these frequencies are caused by short-waveerrors, in which case it
is sufficient to correct the track using thesmoothing method.
However, at higher speeds, faults in trackgeometry with larger
wavelengths also cause considerable dy-namic forces and must,
therefore, be eliminated.
Fig. 1 shows that, at a speed of 160 km/h, faults
withwavelengths of up to 100 m must be taken into considerationand
that, at a speed of 350 km/h, even faults with a 200 mwavelength
cause rolling stock reactions [1]. This correspondswith experience
gained in practice by high-speed rail operatorsand has, recently,
brought about a change in the trackmaintenance strategy adopted by
some railways - changing fromthe smoothing method to the absolute
track geometry method.
Absolute track geometry methodOn high-speed railway lines,
deviations in track geometry fromthe target position have to be
kept to a minimum. High-speedrailways, therefore, use absolute
reference systems for trackgeometry.
In Austria and Germany, from 1972 onwards, fixed referencepoints
were set up, generally on catenary masts, allowing theposition of
the track to be defined in relation to the fixed pointsand the
versines in between (Fig. 2). In other countries, e.g. theUnited
Kingdom [2], France [3] and Switzerland, similarsystems have been
introduced.
TRACK CONDITION MONITORING AND DIAGNOSISTrack condition
monitoring of high-speed railway lines is a taskof major
importance, in order to ensure ride quality and safety.
The basis of all track maintenance operations is an
exactobservation and recording of the state of the track. On
AustrianFederal Railways (ÖBB), for instance, this is carried out
usingthe Plasser & Theurer EM 250 ([4], [5]) and EM 80
trackrecording cars. The core unit on the electronic track
recordingcars of the EM series, which are available for various
recordingspeeds and are in use on a great number of high-speed
railwaylines, is the PAC (Plasser American Corp.) Non-contact
InertialNavigational Track Geometry Measuring System with
opticaldual-gauge measuring system (OGMS).
The PAC Inertial Navigational Track GeometryMeasuring System for
accurate measurement resultsOn track recording cars for high-speed
railway lines, non-contact track geometry measuring systems are
used to enablehigh measuring speeds and ensure accurate and
repeatablemeasuring results. For high-speed railway lines, it is
importantto obtain information about both short-wave and
long-wavedeviations in track geometry. Therefore, chord
measuringsystems, which are based on a limited measuring length,
havebeen replaced by inertial measuring systems that record
aspatial curve. The PAC Inertial Navigational Track
GeometryMeasuring System uses the Applanix POS/TG which, based ona
three-dimensional laser gyroscope combined with GPSpositioning,
delivers accurate position and orientation data forthe precise
measurement of track geometry parameters (gauge,superelevation and
calculated twist, longitudinal profile,horizontal alignment,
curvature and grade), even at low speeds.
The core POS/TG system consists of an Inertial Measure-ment Unit
(IMU) and a POS Computer System (PCS) withembedded Global
Positioning System (GPS) receiver.
Rail Engineering International Edition 2007 Number 1 9
Plasser & Theurer machines and technologies applied fortrack
maintenance of high-speed railway lines: a selectionWhenever the
speed or capacity of a railway line is increased, or a new
high-speed railway line is built,the application of appropriate
track maintenance procedures is very important to enable optimaland
efficient use of these lines, as well as to maintain a high level
of ride quality and safety. Trackmaintenance technologies are
developed continuously to meet the demands of high-speed and
high-capacity railway lines. This article looks at a selection of
Plasser & Theurer machines and technologiesapplied for track
maintenance of high-speed railway lines.
By: Ing. Rainer Wenty, Plasser & Theurer Export von
Bahnbaumaschinen GmbH, Vienna, Austria.
Fig. 1: Reaction-oriented evaluation of track geometryat the
critical frequency of 0.5-10 Hz
Fig. 2: Fixed-point reference system adopted on DB AG and
ÖBB
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Distance Measurement Indicator (DMI) and Optical
GaugeMeasurement System (OGMS) sensors are used to provide
thePOS/TG system with accurate data on distance travelled
andhalf-gauge measurements.
Unlike vertical gyro-based systems, which are notorious forfalse
orientation readings while subjected to centrifugal forcesduring
turns, the POS/TG system provides the user with accu-rate track
geometry output data under all dynamic conditions.During its
operation, POS/TG constantly calibrates the inertialsensors of the
IMU (three accelerometers and threegyroscopes) for improved track
geometry and navigationperformance. This calibration and the nature
of the trackgeometry computation algorithms implemented in
POS/TGresult in the ability of the PAC Inertial Navigational
TrackGeometry Measuring System to construct the track
geometrymeasurements for a wide range of vehicle speeds.
The EM-SAT track survey carBefore any efficient and accurate
track maintenance work canbe carried out, a survey of the actual
track geometry has to bemade by measuring longitudinal level and
alignment.
The EM-SAT track survey car (Fig. 3) enables fullymechanised
measurement of the actual track geometry, using alaser reference
chord. The EM-SAT consists of a main vehicle,equipped with a
computer system and a laser beam receiver, andan auxiliary
(“satellite”) trolley that carries a laser transmitter.Measurements
are taken in a cyclic sequence. The machinemoves forward along a
laser beam, emitted by the lasertransmitter on the satellite
trolley. Any deviations from thetarget track geometry are measured
and recorded. Every 50 to150 m, the satellite trolley stops at a
fixed point and, then, movesforward again. The average measuring
speed (including allstops) is 2.5 km/h.
Besides displacement and lifting values, superelevation andgauge
faults can also be measured. The recorded data and thecalculated
correction values are displayed on the computerscreen on-board the
main vehicle, in a similar fashion as on theALC automatic guiding
computer screen on-board the tampingmachine.
Electronic transmission of data to the tamping machineguarantees
highest precision and, at the same time, prevents anytransmission
faults that can occur in manual measuring.Experience gained on
German Rail (DB AG) has shown anaccuracy of 1 mm, a measuring speed
of 1.5 to 2.6 km/h, and acost reduction of EUR 3.00 per metre of
measured track.
Satellite-supported track surveyingMaintaining fixed reference
points is rather labour-intensiveand, therefore, quite costly.
Furthermore, it is often found thattheir position has changed in
the range of some centimetres.Also, manual measurement of the track
position in relation tothe fixed reference points slows down the
measuring speed, andis also a source of inaccuracy and further
costs.
When building new lines, and when surveying existing lineswith
regard to their general layout, the application of
thesatellite-supported Global Positioning System (GPS) is
alreadystandard technology.
The latest development now is the combined use of EM-SATand GPS
(Fig. 4) to check the track geometry. The simultaneoussurveying of
the actual track geometry using laser referencechords and GPS makes
it possible to transmit the highlyaccurate laser reference chord
data in absolute track co-ordinates.
Incorporation of a ballast profile measuring systemThe EM-SAT
track survey car can further be equipped with anon-contact ballast
profile measuring system, which records theballast profile by means
of a laser scanner. The contour of theballast profile is computed
from the sequence of pulses receivedand stored every 2 m (maximum
speed 15 km/h). On thecomputer display, the measured profile is
superimposed by theimage of the target profile appropriate to the
line, which isselected by the operator at the start of work (Fig.
5). A surplus(green bars) or a lack of ballast (red bars) is
indicated separatelyfor the left and right-hand side of the track,
allowing the ballastprofile to be checked immediately during the
measuring run.The recording results, which can be exported onto a
disc or ZIPfor in-depth office evaluation, enable decisions to be
madeabout the lifts to be performed and the ballast
requirements.
EFFICIENT MAINTENANCE OFHIGH-SPEED RAILWAY TRACKThe maintenance
of high-speed railway track requires a rangeof work processes that
must be coordinated as efficiently aspossible. The better the work
technologies act together, thehigher will be the achievable work
output, the quality of workand, ultimately, the
cost-efficiency.
The mechanised maintenance train (MDZ)Today, it is
state-of-the-art in track construction and mainte-nance to use a
group of machines - a high-capacity mechanisedmaintenance train
(MDZ), the individual machines of which arematched in output,
travelling speed and design parameters, thusforming a harmonic
group of machines. MDZs are available indifferent levels of output;
in each case, the tamping machineleads and determines the output
(Fig. 6).
10 Rail Engineering International Edition 2007 Number 1
Fig. 3: EM-SAT track survey car on Network Rail, United
Kingdom
Fig. 4: Combined use of EM-SAT and GPS
Fig. 5: Computer display showing the measured ballast
profilesuperimposed by the image of the target profile
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To put a track into its correct geometrical position and
toachieve a durable work result requires the following
basicoperations:— track geometry correction, using a
continuous-action levelling,
lining and tamping machine: in 1996, the
continuous-actionthree-sleeper 09-3X Tamping Express was introduced
onÖBB, which features a total of 48 tamping tines, arranged inpairs
and interlaced, thus keeping the ballast penetrationreaction force
to a minimum and enabling optimal squeezeoperation. The standard
work technology of the 09-3XTamping Express is continuous-action
three-sleeper tampingbut, at any time, the units can be changed to
single-sleepertamping operation.
Using the 09-3X Tamping Express, which has a nominaloutput of
2,200 m/h, an increase in average daily output (shiftoutput) from
2.4 to 4 km has been observed on ÖBB, i.e. anincrease of around
42%. This means a much better utilisationof track possessions and,
thus, a rise in the cost-efficiency ofmachine operation due to
lower costs per unit of output.Since all its main lines have been
maintained by three-sleepertamping machines, ÖBB also observed a
substantial increasein track quality. The average track quality
index has im-proved by 21%.
One of the latest machines for high-performance tampingis the
09-4X Dynamic Tamping Express continuous-actionfour-sleeper tamping
machine with integrated dynamic trackstabilisation, which has a
nominal output of 2,600 m/h;
— ballast profiling, using a ballast regulating machine:
con-sidering that one kilometre of conventional double trackholds
between 3,000 and 5,000 m3 of ballast (depending ontype and spacing
of the track), the absolute necessity foreconomical handling and
management of this valuable assetbecomes evident. Some sections of
a track may lack ballast,while others have a surplus. So the goal
has to be to regainthe surplus ballast and add it to where it is
needed. Ballastregulating machines combine the task of ballast
distributionand profiling.
Standard ballast regulating machines reshape the ballastbed by
performing several runs backwards and forwards.However, with the
development of continuous-actiontamping machines, it became
necessary to re-design theballast regulating machines also.
Thus, “one pass” continuous-action ballast regulatingmachines,
such as the USP series, featuring a ballast storagecapacity of 5-15
m3, were introduced. The machines arefitted with large-scale
hoppers that enable a better distri-bution of the ballast and,
thus, achieve savings in new ballast;
— final compaction and homogenisation of the ballast bed, usinga
dynamic track stabiliser: ballast profiling is followed by
trackstabilisation using a Dynamic Track Stabiliser (DTS), whichhas
the task of re-stabilising the track following maintenance.This
reduces the resistance to lateral displacement by around50%.
Contrary to the natural settlement caused by trainloads, the
application of the dynamic track stabiliseranticipates the initial
settlements in a controlled mannerwithout altering the track
geometry. After tamping work, thedynamic track stabiliser lowers
the track as required,gripping the rail heads with roller clamps
and setting thetrack into horizontal oscillation. At the same time,
each railis pressed down in accordance with the readings of
thelevelling device and the superelevation gauge.
The dynamic track stabiliser produces an uniform
initialsettlement that is equal to a load of approx. 700,000
to800,000 tons. Thus, the range for further settlements
isrestricted and the corrected track geometry is preserved
forlonger. The result of this is an extension in
maintenanceintervals of approx. 30%.
On German Rail (DB AG), a long-term trial to determinethe effect
of dynamic track stabilisation on the developmentof track quality
was conducted on a main-line track ofaverage condition near
Regensburg [6]. After tamping, inSeptember 1999, the track quality
was improved by around25%. In January 2001, i.e. 16 months later,
the track sectionthat had been stabilised still showed an
improvement of 21%,whereas the other track section that had not
been stabilisedhad dropped to 8% improvement (Fig. 7); thus, a
longerdurability of stabilised track is obvious.
Maintenance of high-speed switches and crossings usingthree-rail
lifting and four-rail tamping machines (Fig. 8)The use of switch
tamping machines featuring three-rail liftingand four rail-tamping
ensures safe handling of high-speedswitches and improves the
durability of track geometry cor-rection achieved [7].
Rail Engineering International Edition 2007 Number 1 11
Fig. 6: High-capacity MDZ featuring a Tamping Express 09-3X as
the lead machine
Three-rail liftingHeavier designs of switches and crossings, due
tothe use of concrete sleepers and heavy railprofiles, demand
additional measures for theirtreatment. When lifting such turnouts
in thearea of the long sleepers, using the standardtwo-rail lifting
unit, the reaction forces on therail fastenings exceed their yield
strength. Thiswas first detected on DB AG and, therefore,
anadditional lifting arm was developed for switchtamping machines
[8]. Using this additionallifting arm, the diverging rail is
liftedsimultaneously with the rails of the throughtrack, thus
avoiding undue stress on railfastenings and sleepers. Today,
three-rail liftingis a standard feature on switch tampingmachines.
On most railways in Europe, three-rail lifting of turnouts
featuring concretesleepers is mandatory.
Four-rail tampingIn addition to three-rail lifting, the
introductionof four-rail tamping brought a furtherimprovement in
the quality of switchmaintenance.
Fig. 7: Results of a track quality trial (with/without dynamic
trackstabilisation (DTS)), conducted near Regensburg, Germany
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The Unimat 08-475 4S, for instance, features four tampingunits.
The outer units are mounted on telescopic arms, allowingthe tamping
tools to reach a distance of 3,200 mm from the trackaxis. This
enables both the through track and the diverging trackto be tamped
in one operation. Thus, there is no danger that theswitch may
tilt.
CONCLUSIONSIt is worthwhile investing in high-tech machines
featuring soph-isticated work units. The output of the machines for
track layingand maintenance has increased significantly and, more
andmore, use is made of intelligent control circuits. This has
adecisive effect on the cost-effective performance and the
qualityof the work performed.
The focus is always on the long-term effect of a
maintenanceoperation and, at the same time, optimisation of the
costs.
As they ensure that a high level of maintenance is upheld,new
high-technology machines contribute to the sustainabilityof the
investments in high-speed railway lines.
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quality’, Paper
presented to the Working Committee on Railway
Technology(Infrastructure) of the Austrian Society for Traffic and
TransportScience (ÖVG), 8 November 2004.
[2] Spoors R.: ‘Introduction of fixed point based track
geometrymaintenance in the UK’, Rail Engineering International,
Edition2004, Number 4, pp. 12-16.
[3] Le Bihan A.: ‘Track geometry maintenance on high-speed lines
-SNCF’s experience’, Proceedings 15th International ÖVG Con-ference
“Optimising the wheel/rail system - quality, cost efficiency
&financing”, Salzburg, Austria, 14-16 September 2004.
[4] Presle G.: “The EM 250 high-speed track recording coach and
theEM-SAT 120 track survey car as networked track geometrydiagnosis
and therapy systems’, Rail Engineering International,Edition 2000,
Number 3, pp. 14 and 15.
[5] Hanreich W.: ‘Modern permanent way inspection using the
trackgeometry recording coach EM 250’, ZEVrail, September 2004,
pp.18-27.
[6] Lichtberger B.: ‘Longer maintenance cycles achieved by DTS’,
TrackCompendium, 2005, pp. 490-491.
[7] Lichtberger B.: ‘Careful and cost-effective installation,
surveyingand tamping of high-capacity switches: a selection of
Plasser &Theurer machines applied’, Rail Engineering
International, Edition2004, Number 3, pp.11-14.
[8] Lichtberger B.: ‘Die neue Weichenstopftechnologie’,
ETR-Eisenbahntechnische Rundschau, No. 11/1992, pp. 759-762.
Fig. 8: Tamping of a high-speed switch in France
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