Helmut MisarTechnical Information Department,Plasser & Theurer, Austria

E VERY kilometre of a conventionaldouble-track line has between 3000and 5000m3 of ballast, depending on

the type of permanent way and the trackspacing. The economical handling andmanagement of these huge quantities ofmaterial pose a great challenge for trackmaintenance contractors.The ballast is required to distribute the

load from the sleepers as uniformly aspossible over the foundation, to give thesleepers and track sufficient resistanceagainst lateral and longitudinal movement,and to keep the track dry by providing thebest possible passage for the circulation ofair and water run-off.During maintenance, the target geometry

of the track or the switch should be restoredwithout substantial exchange of track ma-terials. This is performed using levelling,lining and tamping machines. The ballastcross-section is formed by ballastprofiling machines.A knowledge of the quantities

of ballast in the track is the startof efficient ballast management.Machines can be equipped with alaser measuring system and anintegrated computer evaluationto measure the ballast profile.A laser scanner acts here as a

non-contact measuring system,scanning the track in twodimensions. When the laserpulse hits the ballast profile, itis reflected and registered inthe laser receiver. The contourof the ballast profile is calcu-lated from the sequence ofpulses received and the evalua-

tion performed in the unit.The measured profile can be superim-

posed on the target profile on the computerscreen. This enables the ballast ploughoperator to select the ideal positioning ofthe plough shares or insert ballast from ahopper. The computer also displays theballast surplus or deficiency as a bar chart,for example.Using such equipment to monitor the

ballast profile enables extremely cost-effi-cient ballast management. A ballast profil-ing machine with sweeper unit and ballasthopper is required to pick up and deposit theballast at the appropriate spots (Figure 1).The AFM 2000 automatic track finishing

machine is the first to provide all thesefunctions. It has been working on AustrianFederal Railways (OBB) since 1998 as partof an MDZ 2000 Mechanised MaintenanceTrain.When the profile measuring device is

mounted on a track recording car, such as anEM-SAT 120, it is possible to plan ballastmanagement in advance by selecting theappropriate ballast ploughs (with or withouta ballast hopper) and by calculating on a PCthe exact volume differences which can bedisplayed and processed.During ballast work, the ballast is re-

arranged, so it might be worth assessingballast quality, especially on the shoulders,at the same time. The production of so-calledradargrammes enables the ballast situationto be recorded very accurately.Using special antennae, extremely short

electromagnetic pulses (300 to 1000MHz) areinjected into the track ballast. These pulsesare reflected on the edges of ballast layers orindividual objects and then conditioned byspecial software. When the data has beenprocessed, the exact layer-by-layer image ofthe track is displayed continuously on themonitor to show damage spots, fouling, and

order of layers.With the Geo-Radar system

developed by Wiebe, which isnow known as GeoRail, an addi-tional profile is produced on thetrack side as well as the normalprofiles in track axis and on thefield side. The sensors can pene-trate to a depth of up to 4m.Another special antenna servesas a ‘‘ballast magnifying glass’’.With a penetration depth of 1.4mit offers an even higher verticalresolution.The four profiles per track are

produced concurrently at a speedof 30km/h. The output per shiftis up to 200km. Four recordingscorrespond to 800km of recorded

Track authorities and vertically-integrated railways can achievemajor savings in trackmaintenance costs by adoptingintelligent ballast managementwith the aid of the latesttechnology in ballastdistribution and profiling.

Track Maintenance

IntelligentBallastManagementWillCutCosts

Figure 1: Display of ballast profile and related ballast quantities.

This Amtrak machine has a material conveyor and hopper unit to increase capacity.

Reprinted from theAugust 2002 issue of International RailwayJournal

profiles. The layout structure is docu-mented without interruption.The physical horizontal resolution,

which is very important to assessfault spots, covers seven to 10 sepa-rate scans per linear metre. Each scanis produced from around 1000 trans-mitted pulses. This makes it possibleto display the layout sharply on ascale of 1:500 (standard 1:2500). Thisis imperative to evaluate the ballastquality and document fault spots.Measurements on the field side and

track side indicate a general tendency:sometimes the track axis appears tobe fouled, whereas the field sideshows a clean and clearly reflectingcontinuous lower edge of the ballast.Therefore the track axis is moreheavily fouled due to operating cir-cumstances. The shoulder is generallycleaner or the shoulder may have beencleaned. The same applies for the track side.Thus the ballast available there is a good

starting material for inserting the ballastfrom the shoulder or from the middle sectioninto the tamping area of the track.The radargramme example (Figure 2)

shows a uniform fouling in the track axis(top) and a cleaned shoulder (below).The following statement appears in a

German Rail (DB) text book: ‘‘To producethe ballast cross-section heavy demands arealso made on modern ballast profilingmachines.’’ As cost becomes increasinglyimportant, ballast profiling machines haveto fulfil the following criteria:. rapid availability. high working speed, adapted to three-sleeper tamping machines or other high-capacity machines. high sweeper capacity with excellentperformance. ballast storage facilities. continuous working action and exact re-profiling of the ballast cross-section in onepass, and. compliance with the applicable standards(CEN).DB’s permanent way guidelines state:

‘‘For work on the ballast bed, the ballastembankment should be produced with thenatural angle of repose (1:1.25). The designof the ballast cross-section should be basedon a cross-fall of the ballast embankment of1:1.5.’’ Depending upon the line speed, thesleepers must be ballasted around the endsby 0.4 to 0.5m (plus a maximum of 0.1m).Due to the tolerance of the slope of the

ballast embankment in the specified ballastcross-section, it is possible to plough theballast upwards into the tamping area anddistribute it in the ballast crown area. Theshoulder angle for the cross-fall is betweenabout 31 and 38o (measured from thehorizontal).Over time, the shoulder angle following

maintenance will flatten due to environmen-tal influences and traffic, so ploughing cancounteract uneconomical widening of theballast bed. Due to the differences in theshoulder angle, ballast can be reclaimed forre-use in other areas. Therefore, the ballastwithin the standard ballast cross-section canbe managed extremely cost-effectively.Ballast profiling in the central section of a

double-track line requires a slewing limita-tion of the side plough. With the help of acomputer-based measuring device, theshoulder plough can be operated in thisarea without problems. Once the trackspacing is defined, the electronically-controlled measuring unit only allows aworking width which does not foul thestandard clearance gauge of the adjacenttrack and enables unhindered travel on theadjacent track. Recovered ballast from thecentral section can also be utilised. When theslewing limitation was introduced in 1986-87, it was estimated by DB that around990,000 tonnes of ballast could be reclaimedannually from the central section.The shoulder ploughs of Plasser &

Theurer’s profiling machines fully complywith the operational requirements. In thelow position, they are extended to the sidesand not folded down. This also ensures thatthe plough slewing movements do not affectthe adjacent profile. The ploughs have alarge adjustment range from 0 to 45o, and anadditional adjustment range over the hor-izontal of around 10o for operations instations. To enable relatively small settingangles that favour the ballast flow in theascending area, the side ploughs have a longplough share. Some models are fitted withoptional equipment to clear the side areausing movable end plates or a rotatingbrush.Symmetrical plough shares with feeder

plates on both plough sides enable work ineither direction. Telescopic designs also

allow operation even on a supereleva-tion of up to 150mm on the outer sideof the curve.Sharp-edged ballast is brought into

the tamping area by ploughing anddrawing up the ballast from theshoulder to the ballast crown. Thiscirculates material in the ballast bedso that practically new ballast isavailable for the next tamping opera-tion, thereby maximising intervalsbetween tamping.Ploughing the shoulder and clear-

ing the side path helps to combatvegetation growth. However, as thisconsists mainly of treating the upperlayers of ballast, accumulations ofhumus in the ballast bed or any deeproots will not be reached.Front or middle ploughs, which are

used to treat the upper ballast bed, aredesigned in V-shape and carry out

simple jobs, whereas centre ploughs in across plough design can work in bothdirections and perform complex tasks.Usually a middle plough is used on high-

capacity ballast profiling machines to takeup the ballast from the shoulder ploughsand distribute it along the trackbed. Thismakes it possible to move ballast across theentire trackbed, from one shoulder to theother, or from the shoulder to the centre areaor vice versa. In one combined operation,ballast can be ploughed away or ballastadded wherever required.Ideally, the tamping area is filled. By

appropriate height adjustment, a maximumof one grain size over the upper edge ofsleeper should remain. Additional baffleplates, adjustable longitudinally, improvethe ballasting of the tamping zone andprotect the track conductor lying in themiddle from damage caused by undesirableballast flow. A channel covering protects therail and the fastenings, but still allows theballast to flow. Control of the plates enablesrapid adjustment of the ballast flow.Partial application in switches and cross-

ings is possible due to the plough halvesbeing split down the middle longitudinally.After tamping and ploughing it is im-

portant, especially on lines with a maximumspeed of above 140km/h, to sweep thesleeper surfaces and ballast cribs thoroughlyusing the sweeper unit to prevent ballastbeing swirled up when trains pass at highspeed.The profiling machine can be equipped

either with a sweeper unit with transverseconveyor belt or, if there is a ballast hopper,with a sweeper conveyor unit which movesthe material via a steep conveyor belt to theballast hopper. From there it can be placedin areas which lack ballast. On machineswithout a ballast hopper the surplus materi-al is deposited on one of the flanks by thereversible transverse conveyor belt.

Track MaintenanceFIGURE 2: RADARGRAMME

Reprinted from theAugust 2002 issue of International RailwayJournal

The rotating sweeper brush is poweredhydrostatically with optimum turningcapacity at high torque and with step-less speed adjustment. A rapid changesystem allows speedy conversion of thebrush shaft, enabling rapid reaction to theprevailing sleeper shapes or the need forlower sweeping in sleeper cribs between therails.On lines with a maximum speed above

140km/h, the sleeper cribs between the railsshould be swept out 3 to 6cm lower than theupper edge of the sleeper. The machine canbe equipped with a dust-arresting sprinklerto dampen dust during sweeping. A secondsweeper unit is recommended to achievehigh working speeds. The first sweeperbrush performs the rough work and thesecond one the fine work.Plasser & Theurer ballast distributing

and profiling machines can be equippedwith ballast hoppers ranging in capacityfrom 5 to 13m3. With a density of 1.65tonne/m3, this is equivalent to 8.25 to 21.5 tonnes.At current ballast prices, such quantities ofballast are worth around Euros 90 to 220.

Ballast recovery is actually a side effect ofthe ploughing and profiling work. However,ballast distribution and profiling machinesthat do not have a ballast hopper can onlydisplace the ballast in the immediate vicinityand produce the desired profile, whereas ahopper enables quantities of ballast to bemoved where it is needed. This also avoidsseparate runs with ballast trains.Amtrak took ballast management a step

further with the introduction of the BallastDistribution System (BDS). The holdingcapacity of the unit can be enlarged asrequired by adding material conveyor andhopper units.This system consists of two machines

operating independently. The front machinesection has a ballast metering unit, aplough to work on the ballast crown, andshoulder ploughs. An integrated ballasthopper has storage capacity of 25m3. Thesecond machine carries the sweeper unit andthe conveyor belt which transports theballast to the hopper and the hopper unitsin between.The BDS was introduced in May 1991. As

a result, Amtrak was able to reduce itspurchase of new ballast by 71% during theremainder of that year, a saving of aroundUS$ 360,000, which is equivalent to about34,000 tonnes of ballast. Other benefits werethat Amtrak did not require work trains,gangs to unload the ballast, or othermachines to profile the ballast bed. Amtrakestimates the system paid for itself withintwo years.Today, high-capacity ballast distribution

and profiling machines operate in contin-uous working action and combine allindividual functions in one work sequence.Depending on the individual requirementsfor output and storage capacity, machinesare now available with a total mass of 15 to85 tonnes and with two to six axles.The ballast distribution and profiling

machine is an important part of a mechan-ised maintenance train (MDZ), led by alevelling, lining and tamping machine, anddesigned to keep pace with the increasinglyhigher outputs of the tamping machines.Universal or switch tamping machines

with a sweeper-conveyor unit and ballasthopper have proven their worth by havingballast available in the switch area.A combination of the dynamic track

stabiliser with front ploughs and sweeperunit at the rear have been designed for trackmaintenance in Japan, as has a similarcombination for the maintenance of high-speed lines in France.Using intelligent ballast management

systems has the potential for large reduc-tions in the amount of new ballast that needsto be purchased annually and thereby avoidthe associated transport and unloadingcosts. The irregular distribution of ballastalong the track also represents a source ofpotential savings. There is too much ballaston many sections of track compared withthe standard profile which could be re-distributed. Track renewal, with a change ofsleeper type and ballast profile, can alsocause a surplus of ballast, either due to thelarger sleeper cross-section or a change ofthe standard profile. IRJA universal ballast distribution and profiling machine operated by DB Bahnbau.

Plasser’s AFM 2000 automatic track finishing machine in operation on Austrian Federal Railways’ network.

Reprinted from theAugust 2002 issue of International RailwayJournal