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In the first part of a comprehensivearticle, Dipl.-Ing.
Christoph Kuttelwascher,
Track Expert, ÖBB-Infrastruktur AG, Vienna,Austria and
Dipl.-Ing. Michael Zuzic, formerHead of Track Division, ÖBB,
Vienna, Austria,describe how track ballast can affect the wholerail
infrastructure. Literary references (thebracketed numbers) will be
detailed in theconcluding part of the article.
Regarding cost-effectiveness and longevityof the rail
infrastructure, the ÖBB’s closecooperation with Austrian and other
Europeanuniversities, as well as civil engineers, has a
longtradition. This enables an efficient utilisation ofknowledge
resources and their combination withpractical experience and the
prevailingknowledge [1, 2] is complemented by newaspects. Examples
given in this article comefrom references and extracts from
investigationsthat were carried out on the topic of track ballastby
Graz University of Technology, MunichUniversity of Technology,
Innsbruck University orHTL (technical college) Saalfelden at the
requestof Austrian Federal Railways (ÖBB).
1. Functions and requirementsIn combination with other track
components,subsoil, drainage and elastic components, thetrack
ballast is a significant component thathas a great influence on the
quality anddurability of the track. The main functions oftrack
ballast and ballast bed can besummarised as follows:n Load
distribution and triaxial loadtransfer.n Resistance against sleeper
displacementin all directions.n Simple restoration of the original
trackgeometry.n Drainage and maintenance of the load-bearing
capacity of the subsoil.n Retention of rainwater.n Ventilation.
From these functions, there is a range ofrequirements to be met
by the quality of theballast itself. In view of the rising
stressesdue to higher axle loads, and numbers oftrains and
travelling speeds on the main lines,the aim is to improve the
resistance of thetrack components to the influences and toincrease
their service life.
An increase of the resistance is achievedusually by improving
the material quality andby technological advances in
themanufacturing process. With trackcomponents such as wooden
sleepers ortrack ballast, the railway has to rely primarilyon
natural resources and/or geologicallydeveloped structures. Track
ballast isproduced by blasting, breaking-down andscreening of solid
rock and can generally onlybe mined where the rock deposits are
notcovered over by loose sediments such assand or gravel. The rock
deposits that can befound in Austria are listed in section 2.
Solid rock for producing track ballast shouldfulfil the
following conditions:
n Resistance to weathering and lowcrack formationThe resistance
to weathering must be verified byappropriate expert reports.
Numbers, spacingand widths of cracks in the rock have a
greatinfluence on the fatigue strength of the rock.
When blasting solid rock by explosives, therewill be crack
formation in various forms andsizes. If micro fissures are not
completelyeliminated in the further reconditioning process,this can
reduce the strength and resistance ofthe track ballast. For the
highest quality andproductivity, the extraction and processing
ofraw materials must, therefore, be adapted tothe respective rock
and its place of occurrence.
n Toughness, hardness and lowcleavabilityThe toughness is the
resistance to breaking orexpansion of cracks and can be expressed
byload-deformation graphs. Crack deflection, crackbranching or
crack stop ability are influencingfactors here [3, 4]. The hardness
of a rock is theresistance to mechanical penetration and is
theresult of mineral hardness, grain binding andhardness of the
binding agent between theminerals. The minerals are arranged
accordingto the size of their Ritz hardness using the Mohshardness
test.
For minerals, the cleavability refers to thetendency to break at
certain parallel planes inthe crystal lattice. The strength of a
rock isenhanced by mineral constituents of low orlacking
cleavability. Biaxial or triaxial cleavableminerals have a negative
effect on thestrength [5].
n No additions of loam, earth or fine particlesAfter rainfall,
the ballast bed must dry out asquickly as possible and this is
onlyguaranteed ideally when there is a high levelof air
permeability. Larger quantities of fineparticles hinder the
drainage capacity of theballast which in the long term can have
anegative effect on the load-bearing strength ofthe subsoil. In
addition, fine particles, whichin wet condition encase the
load-distributingparticles like a lubricant, reduce the
frictionangle and thus lower the shearing strength(see 6.2).
n Good breaking behaviour (e.g.sharp edges)The better the
breaking behaviour, the greaterthe interlocking of the ballast
stones to eachother and to the sleepers which, in turn,produces
more favourable load transferproperties and higher resistances to
longitudinaland lateral displacements of the track.
2. Geology and rock deposits in Austria
The following types of rock are used in Austriafor the
production of track ballast.
n GraniteThe greater part of the Bohemian Massif liesto the nor
th of the Danube andaccommodates large deposits of granite
fromwhich track ballast is produced. Granites aredeep-seated
magmatic rocks which areformed under high pressure and at
hightemperatures. They are medium to coarsegrained and usually
their crystals can berecognised with the naked eye. Their
highcolour variability is usually determined by thecontent of
feldspar and the colour spectrumranges from light grey to bluish,
and reddish-pink and orange to yellow.
The yellow colours of granite can alsooccur due to weathering of
ferriferousminerals (e.g. haematite) to limonite orthrough
weathering of feldspars to clayminerals (kaolinisation). Yellow
granites areusually technically poorer than grey granites.Selective
mining and regular checks of theweathering indicators are of great
significancehere. However, discolouration processes canalso occur
due to ore minerals contained inthe rock without the technical
propertiesbeing altered detrimentally.
Due to their origin, quartz-rich rocks canshow a higher
susceptibility to impact (quartzcrack). However, in carbonate rocks
the additionof quartz increases the compressive strength. Ahigh
proportion of larger feldspars and mica canhave a negative
influence on the strengthproperties due to their complete
cleavability [5].
n Granite porphyrIn Austria, in the transition between
theBohemian Massif and the Molasse zone,there are deposits of
granite porphyr whichare also suitable for track ballast
production.Granite porphyr is a kind of granite but ofporphyric
structure. In the fine-grained todense basic mass, there are
greater lightfeldspar crystals or brown biotite platesstored which
can be seen with the naked eye.Due to the dense structure, there
will often bea metallic sound when struck by a hammer.
n GranuliteGranulite deposits occur in the old primary
rockmassifs such as in the Moldanubicum of theBohemian Massif in
the north of Austria(Waldviertel). Granulites are
metamorphosicstones that have occurred under mediumpressure and
high temperatures. Their maincomponents are feldspar and
quartz,sometimes containing (brown-red) garnets thatcan be
recognised with the naked eye in theoften white to dark grey or
brownish granulites.Granulite obtained its name from the
Latingranulum which means grain. This refers to theusually
fine-grained to medium-grained structure(finer than granite) and
the uniform texture.
Granulites are suitable for use as trackballast due to their
high compressive strengthand very high resistance to wear.
Thegranulite deposits in the Dunkelstein Forestare partly veined
with serpentinites. However,these are easy to recognise visually
and canbe eliminated by selective mining.
n DiabaseDiabase occurs due to metamorphosis(transformation
processes under the influence ofpressure and temperature) of
basalts. Only fewdiabase deposits in Austria fulfil the
stringentsuitability criteria for track ballast (e.g.
northernGrauwacken zone and Bleiberg Hochtal). Thedark green to
black-green colour is producedfrom the first stages of
metamorphosis which isthe reason why earlier diabase was often
calledgreen stone. The proportion of chlorite occurringdue to
chloritization is decisive for the strengthbehaviour. In the
vicinity of the Bleiberg Hochtaland the Gailtal, diabase with a
reddish colour ismined and this colouring is due to minerals suchas
haematite or magnetite. No detrimentaleffects on the strength
properties havebeen noted.
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Track ballast in Austria: Part 1.
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Diabase is dense to medium-grainedand sometimes the rock
develops a
porphyric texture due to embedded feldspar.
n BasaltBasalt is a basic volcanic igneous rockoccurring as
watery lava when it erupts at theearth’s surface. It consists
primarily of amixture of iron and magnesium silicates witholivine
and pyroxene and calcium-richfeldspar. It is normally dark grey to
black,whilst brownish, reddish or grey-greennuances are also
possible, and consists forthe most part of a fine-grained
elementarymatter. Due to its very high resistance topressure and
wear, basalt is generally verywell suited for track ballast
production.
Excepted from this are basalts with atendency to sunburn.
Sunburned basalt isextremely susceptible to
weathering,disintegrates easily and is, therefore, notsuitable for
many technical applications.Sunburn endangered basalt is excluded
fromdelivery to the ÖBB.
In Austria, basalts only occur in the eastand south-east
(Burgenland, Styria andCarinthia) and here the occurrence cameabout
in three volcanic phases. The mostprofuse phase is found in the
south-eastStyrian vulcano region [4].
n Dunite, peridodite and bronziteIn the middle
Austro-AlpineGrundgebirgsdecke of Styria, there areultrabasic and
ultramafic rocks with variousdegrees of serpentinisation. Rocks
classed asultrabasic are those with a SiO2-content ofunder 45%.
Ultramafic is a term given toportions of rocks with over 90% dark
mineralsof the magmatic rocks [7].
At least 90% volume of dunites consist ofolivine, in comparison
to the peridotites thatconsist to 40% to 90% by volume of olivine.
Asfar as the technical utilisation is concerned,the degree of
serpentinisation is of decisivesignificance. Dunites and
perdidotites havegood strength properties as long as
theserpentinisation is not too far advanced,whereby high contents
of hornblende andaugite raise the toughness of the stone.
Serpentinised dunites are mainly darkgreen to black-blue,
whereas serpentinites arebrown and brown-grey to black.
Bronzites are very tough, medium
to coarse-grained rocks with greenish brown colouring.
n Limestone (dolomite)Limestone is a sedimentary rock usually
ofbiogenous origin. However, it can also beseparated from water by
chemical processesand consists mainly of calcium carbonate.
Inportions, other minerals are also presentsuch as clay minerals,
dolomite, quartz andgypsum. If the dolomite portion
predominates,then it is generally regarded as dolomite ordolomite
stone.
The stone properties and, therefore, alsothe technical
utilisation of limestone can varygreatly. Whereas dolomites and
limestonesare often classed as medium-hard rocks,there are
silicious limestones that arecategorised among the hard rocks.
Thesilicification improves the mechanicalresistance which is
expressed in the fact thatthe compressive strength is up to twice
ashigh (compared to limestone). Gravellimestone deposits in
Switzerland are usedthere for the production of track ballast.
In Austria, the northern Limestone Alpsstretch from Vorarlberg
to Lower Austria andconsist mainly of limestone or dolomite. For
theproduction of track ballast, these rocks are onlypartly suitable
due to their strength properties.
3. ÖBB conditions of deliveryTrack ballast is a natural product
and is,therefore, subject to fluctuations in quality. Toguarantee
the durability of track ballast over along service life, only hard
rocks are used inthe Austrian core network. For a long time,rocks
were allocated to this group through thedefinition of cube
compressive strength, thecontent of hard minerals (hardness
scaleaccording to Mohs) or the suitability for use asdouble-broken
chippings. The criteria forsuitability as track ballast material
are giventoday from the requirements of the ÖBBSupply Conditions
[8] on the basis of theEuropean standard EN 13450 [9].
In 2011, the ÖBB drew up a testingsystem concerning the
‘production and supplyof track ballast grain size I and II’ [10].
Thisoffers the possibility to test the suitability ofthe quarries
even without a firm order. Thenthe qualified suppliers can be
called directly to submit offers. Basically, a distinction ismade
between geometrical, physical and
chemical requirements.
3.1 Geometrical requirementsThe chosen grain size distribution
mustguarantee a suitable load dispersion, loadtransfer and
drainage. Close-grained aggregateshave a positive effect on the
drainage capabilityand the elastic properties. However,
withincreasingly narrower grading, the shearingresistance also
drops which is accompanied bythe more unfavourable load transfer
propertiesof lower ballast bed stability.
It is here that the particle shape hasspecial significance (due
to its equalisingfunction). It can equalise the above
mentionednegative aspects of a narrow grading and,therefore, due to
the interlocking of theballast stones, the stability is retained
even inthe case of close-grained material. However,there will
inevitably be peak pressures andconsequently the edges of the
stones will bebroken or chipped off.
Dynamic track stabilisation anticipatesstone rearrangement
processes and leads tosettlements during operation. This raises the
number of contact points between theballast stones and, therefore,
reduces thepeak pressure.
The granulation K1 (31.5/63) used inAustria, seen in Figure 1,
tends towards (inthe same way as the granulation for trackballast
in Germany) the category Gc RB B(formerly category D) of EN 13450
[9]. Forreasons of worker protection, track ballast ofgranulation
K2 (16/31.5) is used whereverthe workers have to enter the track
regularly inorder to carry out work on the vehicles (e.g.parking
and marshalling areas).
The proportion of fine particles (< 0.5mm)and finest grain
(< 0.063mm) is limited to amaximum of 1.0M% because fine
particles inlarger quantities can hinder the drainage andalso
reduce the shearing strength of the ballastbed (see 6.2). Despite
correct screening, onopen storage depots fine grain fractions
fromthe upper and middle piles may be washed intothe lower sections
of the pile of material andcollect there due to precipitation. In
the case offunnel discharge or transport using wheelloaders, it is
possible that these areas, inparticular, are loaded in a
concentrated way.Therefore, in Austria, it is mandatory to performa
screening of the entire ballast materialimmediately before the
loading process. In mostcases, the product will be washed at the
sametime for additional reduction of the fineparticles, whereby it
is necessary to adapt theflow of water to the material throughput
at thevibrating screen. If low-dust ballast is requiredfor special
applications (e.g. tunnels), thecontent of finest grain must not
exceed 0.5% inweight and at all times only washed ballastshould be
used.
To avoid any possible grain fragmentationand demixing during
loading, transport andunloading, it is stipulated that when
takingspecimens on the worksite the undersizeportion must be <
22.4 mm or a maximum 5%in weight (maximum 3% in weight in the
quarry).
The particle shape is determined incompliance with EN 933-4 [11]
and the resultis given as the particle shape index. Theproportion
of stones with a ratio length:width> 3:1 must be between 5 and
30% in weight,carrying out the test on particle groups
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64 RAIL INFRASTRUCTURE
Left: Figure 1: Grading curve of thegranulation K1 (31.5/63 mm)
(Source: [8])
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31.5/50mm and/or 16/31.5mm.The length of the stone is verified
by
measuring using appropriate particle shapecaliper gauges. On a
specimen of more than40kg delivery granulation (31.5/63mm), themass
portion of grains with a length ≥ 100mm shall be 6% at the
most.
3.2 Physical requirementsn Impact-attrition strength (LosAngeles
coefficient)The impact-attrition strength is determinedaccording to
the Los Angeles testing methodin compliance with EN 13450 [9] and
EN1097-2 [12].
To carry out the test, a specimen of 10kg(grain size 31.5/50)
following washing anddrying is placed in a steel drum(approximately
70cm diameter), together with12 steel balls (total weight
approximately5.2kg) and rotated 1,000 times around itsaxis. The
speed of rotation is around 30revolutions per minute. During
rotation, thetest material is lifted by a ridge on the innerside of
the drum and thrown down again. Themechanical stress on the rock is
by bothimpact and attrition through the interactionsof steel balls,
stones and drum wall. Figure 2shows a stone specimen before and
aftercarrying out the test, Figure 3 shows a cross-section through
the Los Angeles drum.
The Los Angeles coefficient LARB is
obtained after screening through a 1.6mmsieve according to the
formula:
LARB= 10.000 - m100
Note: m = material passing through the1.6mm sieve.
The lower the Los Angeles coefficient, themore resistant the
rock is to impact andattrition stress. Generally, only rock with
LosAngeles coefficients of a maximum of 22% inweight are utilised
as track ballast in Austria.Typical LARB values of different track
ballastrocks in Austria are shown in Figure 8.
n Impact strength (impactfragmentation value)The resistance to
fragmentation is determinedin compliance with EN 13450 and EN
1097-2[12]. The impact fragmentation coefficient SZRBis obtained
from the mean value of threeseparate operations. In each case, a
mass ofaround 2.8kg (grain size 31.5/40) is placed ina mortar (17cm
inside diameter) after washingand drying and stressed by twenty
blows of adrop hammer. The hammer has a mass of 50kgand falls from
a height of 42cm. The rockfragmented when this test is carried out
is thenpassed through the 8mm sieve.
The stress on the rock has an impactcharacter and the resulting
fractured stone isobtained from the striking energy of the
drophammer on to the specimen. Figure 4 shows
a stone specimen before and after carryingout the test. Figure 5
shows a typical impacttesting device.
The impact fragmentation value iscalculated according to the
formula:
SZRB= M1M
Note: M = mass of the single measuringspecimen before the test;
M1 = materialpassing through the 8mm sieve.
The lower the impact fragmentationvalue, the more resistant the
rock is to impactstresses. Generally, only rock with
impactfragmentation values of maximum 22% inweight are utilised as
track ballast in Austria.Typical SZRB values of different track
ballaststones in Austria can be seen in Figure 8.
n Resistance to wear (Micro-Devalcoefficient)The resistance to
wear is determined incompliance with EN 13450 and EN 1097-1
[13].The Micro-Deval coefficient is produced from themean value of
two separate operations.
Each separate measuring specimenconsists of a mass of 10kg of
washed anddried fractured stone 31.5/50. This is placedin a drum
(20cm diameter) filled with 2.0 l ofwater and stressed at a speed
of 100revolutions per minute through friction on theinside wall of
the drum. After 14,000revolutions, the specimen is screened
RAIL INFRASTRUCTURE 65
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Above: Figure 2: Stone sample before and after a Los Angeles
test asper [12] (Source: ÖBB). Above: Figure 3: Typical Los Angeles
test machine (Source: [12]).
Above: Figure 4: Stone sample before and after an
impactfragmentation test as per [12] (Source: ÖBB).
Right: Figure 5: Typical impact testing device (Source:
[12]).
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through a 1.6mm sieve. The Micro-Deval coefficient is
calculated according to the formula:MDERB= 10.000 - m
100Note: m = mass of the material retained onthe 1.6mm sieve, in
grams.
In the Micro-Deval test, the rock is onlystressed by friction.
The rock is more resistantto wear the lower the Micro-Deval
coefficientand, therefore, the greater the materialretained on the
1.6mm sieve. Figure 6 shows arock specimen before and after
testing, Figure7 shows a normal testing apparatus.
Typical MDERB values of various trackballast stones in Austria
can also be seen inFigure 8.
n Gross densityGross density is determined in accordancewith EN
1097-6 [14]. This is the density of theraw stone as a ratio of mass
to volume. Themass is determined by weighing the specimenin
water-saturated and surface-dried conditionand then again in
oven-dried condition. Thevolume contains all pores and
cavitiesspecific to the rock. No test value is laid downfor the
gross density but generally high grossdensities are required.
In contrast to the gross density, the bulkdensity describes the
ratio of mass to volume ofan unconsolidated, dry stone granulation
(loosematerial). It is equivalent to the lowestcompactness
including all bulk and bedrockpores. We know from experience that
it is roughlyequivalent to half the gross density and is,therefore,
around 1.3-1.5 t/m³ for track ballast.
The vibration density is that density of aheap of material that
is achieved by vibration.
This is equivalent to the maximum achievabledry density in
close-grained, coarse aggregates.
n Resistance to weatheringThe stone used as track ballast must
beresistant to weathering. Weathering is aprocess of stone
disintegration due tophysical, chemical or biogenous influencesand
their combinations (e.g. temperaturefluctuations, frost, ice, salt,
acids).
The evaluation of the resistance toweathering can be made in
many differentways - by visual inspection (in the deposit andfrom
broken material), by petrographicexpertise and by undertaking a
number oflaboratory tests. The laboratory tests includethe
identification of water absorption [14], theresistance to freezing
and thawing [15] or theresistance to magnesium sulphate [16].
Ifthere is a suspicion of sunburn in basalt rock,the volume
stability must be confirmed incompliance with EN 1367-3 [17].
3.3 Chemical requirementsThe chemical requirements assure
theecological acceptance of the rock material andare based on the
national regulations concerningrecycling and waste dumping. In
Austria, theseare primarily the Waste Management Act,Federal Waste
Management Plan and LandfillOrdinance. At the end of its technical
lifespan,the used ballast should then be recycled or bedisposed of,
if necessary, at low cost.
3.4 Alternative testing methodsApart from the mandatory testing
methodsconcerning wear and impact strength of trackballast [cp.
18], alternative methods are, inprinciple, also conceivable. On
behalf of
Austrian Federal Railways (ÖBB), studies offive alternatives
testing methods were carriedout at Graz University of Technology
and atHTL Saalfelden (cp. [19]).
The test to determine the compressivestrength in the excavated
material [20] is alarge-scale pressure test using a
containersimilar to an odometer.
Two other testing methods, namely thetest to determine
grindability of rock by meansof a scratch test (Cerchar test) and
the grindingand milling test for granulates (Abroy test),were
developed to estimate the wearing rate onmining tools, but also
enable conclusions to bereached regarding the abrasiveness as
ameasure of resistance to wear.
Using an adapted triaxial test unit with aconstant displacement,
the point load test [21]applies a force until the track ballast
grainbreaks. This also enables conclusionsregarding the
cleavability and the loaddeformation behaviour of the rock being
tested.
In the course of a modified impactfragmentation test [21], a
dynamic load wasexerted on the excavated material with
ballastgranulation K1 (31.5/63mm) using a dropweight under an
initial load of 70kg. Bydefinition, the fine grain enrichment is
dividedinto fragmentation (percentage by mass <22.4mm) and
content of fine par ticles(percentage by mass < 4mm).
All testing methods were carried out in anexemplary way with
specimens of rockssuitable for use as track ballast andcorrelations
were investigated with resultsfrom the established methods. Some of
theresults have been published and furtherdevelopments in the field
of standardisedquality controls can be expected.
66 RAIL INFRASTRUCTURE
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Left: Figure 6: Stone sample before and after a Micro-Deval test
asper [13] (Source: ÖBB).
Below: Figure 7: Usual test device for Micro-Deval test (Source:
[13]).
Above: Figure 8: Test results of important track ballast stones
in Austria, detailing mean values and a scattering of the
mechanicalcharacteristics (2004-2011) as per EN 13450.
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Permanent Way
In the second part of their article, Dipl.-Ing. Christoph
Kuttelwascher, Track
Expert, ÖBB-Infrastruktur AG, Vienna, Austriaand Dipl.-Ing.
Michael Zuzic, former Head ofTrack Division, ÖBB, Vienna, Austria,
describehow track ballast can affect the whole railinfrastructure.
Literary references (thebracketed numbers) will be detailed in
theconcluding part of the article.
4. Stone mining and selective exploitation
In past years, the ÖBB needed around onemillion tonnes of track
ballast annually(fluctuating above and below this figure) inorder
to implement all worksites (renewal andmaintenance). Depending upon
the wagonsused (loading quantity), this is equivalent tothe figure
of around 25,000 to 35,000wagonloads per year. Unlike other
trackcomponents, a high proportion of the price ofballast is
incurred by transport of the materialto the worksite. Besides
technical and qualityassurance aspects, high demands are placedon
daily loading capacities, weekly productioncapacities and long-term
availability in orderto guarantee a reliable worksite supply.
The mechanical requirements to be metby track ballast are the
highest of all rockproducts which automatically limits thenumber of
effective suppliers. Deposits of rawmaterial occur homogeneously or
are veinedwith rock zones of lower quality, depending onthe
geological formation processes. Thesezones can be excluded from the
track ballast production with the help of geologicalsurveys for
thorough underground exploration,exact mining planning and
selectiveexploitation - a precondition for consistentlyhigh-quality
material.
Usually the mining and rock processing forthe production of
track ballast is carried out inthe following main stages: clearing,
boring,blasting, transportation, separation, rough-crushing,
mineral processing, breaking-down,screening, storing,
post-screening and loading.
Normally, the rock is removed from thequarry by large borehole
blasting which cancause cracks in different sizes.
Optimisedborehole spacing and explosive chargesminimise the
occurrence of micro-cracks. Therequired K1 granulation is normally
producedafter the second breaking stage by screeningusing
square-mesh screening on steel orsynthetic sieves. Considerations
are beingmade to break up all micro-cracks completely inthe
reconditioning process because anyremaining micro-cracks in the end
product havea negative influence on the strength properties.
5. Quality assuranceThe ÖBB uses a multi-stage quality
assurancesystem. All suppliers of railway ballast musthave CE
conformity certification and pursue acertified, regular, internal
production controlsystem as per EN 13450 [9].
5.1 Qualification test, inspectiontests, intermediate tests
The qualification test (initial test) enables astatement to be
made whether the materialbeing mined meets the
specifiedrequirements and takes into account all majorparameters of
EN 13450 [9]. Geological,
petrographic and tectonic expert appraisalsgive information
about medium and longerterm rock properties in the mining region
andenable an estimation of the qualitydevelopment in the
future.
The operational assessment itself isperformed by the ÖBB. Expert
opinions andtest results are referred to in the course of
theoperational assessment. Ballast specimensare taken on location
for a further round oftests and the technical and
commercialefficiency of the supplier is assessed.
Inspections (conformity tests) are carriedout by ÖBB officials
in every supply quarry atleast twice a year. They establish whether
thequality properties meet the contractualrequirements and serve as
a conformitycertificate of internal monitoring by themanufacturer.
The ballast specimens taken atthe quarry provide test data that is
collected in acentral system. Figure 8 (see part 1 of thearticle)
shows examples of time series oftypically achieved mechanical
characteristics ofvarious types of rock in Austria.
In trade literature there is often mentionof the good
correlation between LA value andimpact fragmentation value. In
Austria, such acorrelation applies only for a few types of
rock(e.g. basalt) whereas other rocks (e.g.granulite) have no
correlation (cp. [19]). Forthis reason, both testing methods are
used inthe round of tests in Austria.
Intermediate tests (identity tests) serve tomonitor the ballast
quality at the laying site andcan be performed by the ÖBB at any
time. Whenthe quantity delivered is over 1,000 tonnes, atleast one
intermediate test must be carried outon the respective worksite.
For worksites withdelivery quantities of over 5,000 tonnes at
leastone intermediate test must be carried out per1,000 tonnes of
material. Normally the grainsize distribution is checked, but other
stoneparameters can be investigated if required.
5.2 Loading Before ballast is loaded by the supplier, everywagon
must be checked so that it is empty inorder to avoid incorrect
loading or mixing withany possible residue in the ballast wagon.
Thiscan be done by visual inspection or by usingautomatic video
surveillance systems. If thelatter is chosen, it is possible for
the customerto check the loading process in real time.
Figure 9 shows an example of the loadingcontrol of an ÖBB track
ballast supplier usingautomatic video surveillance (start-up in
2011).One image is generated at times of predefinedstages of
loading. Documentation of the wagonnumber and the wagon in an empty
state ismade by two images before loading, thedocumentation of
loading by one image duringactual loading and another one
afterwards.
The automatic recording process iscontrolled by an interface
with the (officiallycalibrated) belt weigher and documents
thecurrent loading quantity. All loading data andphoto information
are stored in real time onthe server to which the customer
(scheduling)has direct access.
6. Load transfer anddimensioning of the ballast bed
6.1 Hertz’s contact pressure at the rail
One of the most important functions of theballast bed is to
absorb and distribute thestatic and dynamic wheel loads and
totransmit them to the subsoil. The wheel-railcontact patch is only
1-3cm2, dependent ontheir lateral position, the wheel loads
appliedand the contact geometry (rail wear). HeinrichHertz’s theory
enables a calculation of thestresses and their distribution to the
contactsurfaces of elastic bodies.
For the calculation of the shearingstress occurring at the
wheel-rail contact
Track ballast in Austria: Part 2.
Above: Figure 9: Images from the automatic loading control of an
ÖBB track ballast suppliershowing the video surveillance at various
stages of loading - documentation of wagonnumber, wagon empty,
loading process and load weight. (Source: ÖBB).
RAIL INFRASTRUCTURE 63
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surface, the following formulae applyaccording to Hertz’s theory
with the
assumption of a roller contact: F•r 2a=3,04•2•b•E
(mm)
Note: F = effective wheel force (N).r = wheel radius (mm).b =
half width of rolling surface (mm).E = modulus of elasticity of the
rail steel (2.1 • 105 N/mm2).PRS = contact pressure (N/mm
2).Under the simplified assumption (only
valid for r ≥ 300 mm) F F• 2•b•E PRS= 2a•2b
= 3,04• F•r•2b (N/mm2)
With E = 2.1•105 N/mm2 and 2b = 12mm(width of rolling surface)
it applies:
FPRS= 43,5• r (N/mm2)The maximum shearing stress �Tmax, that
occurs at a depth of 4mm to 7mm iscalculated according to the
half-space theory.
Tmax = C•PRSC is a factor that lies between 0.31 and
0.33 with constant sur face pressuredepending on the type of
touch surface.
For the maximum shearing stress �Tpermit, therefore, applies by
approximation:
FTmax=0.3•PRS=13,05• r
6.2 Load dispersion in the ballast bed
With an assumed contact surface of 3cm2 andwheelset loads of 225
kN this producespressures of around 42.000 N/cm2 at the
railsurface. With other contact geometries, thesepressures can rise
even higher and must becontinuously assimilated and distributed by
theindividual track components. With a theoreticalsleeper
supporting surface of around 2,400cm2
there will still be pressures, for example on theunderside of
the sleeper of around 37 N/cm2
[23]. However, according to investigations byMunich University
of Technology, the effectivesleeper supporting surface for
uncoatedsleepers after consolidation, depending on thenumber of
load alterations, is only around 1-2%of the total sleeper underside
area. On theAustrian pre-tensioned concrete sleeper K1 thisis
equivalent to around 100cm and wouldindicate very high contact
stresses (up toapproximately 2,000 N/cm2) [24].
A sufficiently large ballast bed isnecessary to distribute the
traffic loads over anadequately large area of the
substructureand/or subsoil and not exceed its load-bearingcapacity.
Due to the rail depressions, elasticelements and irregular support
conditions, aninitial settlement is necessary to distribute
thewheel load over several sleepers and toactivate the underlying
resistance force of theballast bed even under the adjacent
sleepers.The larger the flexural strength of the rail andthe lower
the stiffness of the trackbed, themore sleepers will be needed for
the loadtransfer. The skeleton track itself is a
floatingconstruction in the loose pile of ballast and thetraffic
loads can be dispersed uniformly intothe subsoil only when there
are homogeneoussupport conditions.
The load transfer in the ballast bed iscarried out via the
contact surfaces of ballaststones to each other, primarily
throughcompressive forces and secondarily throughshearing forces.
The assumption of a linear
distribution of pressure according to Fröhlich[25] applies only
for isotrope andhomogeneous materials. In reality, loadtransfer
occurs through randomly formedforce paths (Figure 10).
Depending upon load intensity and depthof the ballast bed,
individual force paths reachas far as the subgrade even outside
theassumed load dispersion angle. To take intoaccount anisotropy
and inhomogeneity,Fröhlich used the concentration factor VK.
The surface pressure on the formationdepends on the assumed load
dispersion angleof the ballast bed. To ideally utilise the
load-bearing capacity, the subsoil (subgrade) and toachieve a
uniform course of pressure on theformation, the depth of the
ballast bed shouldtheoretically be large enough that the
pressuredispersion lines of adjacent sleepers intersectover the
formation [1] is produced from:
n a =2*tan
Whereby a is the ballast bed depth underthe sleeper, n the
sleeper spacing and theload dispersion angle.
Practical experience shows substantialdeviations from a
homogeneous support due toscattering in the initial consolidation,
grainfragmentation as a result of traffic loads or grainsize
distributions altered by entry of foreignmaterial (e.g. airborne
dispersal, spillage). Whenlaying new track, it is especially
important toproduce a ballast structure in the form of a
high-quality, homogeneously compacted ballast bed.
When considering the defined target heights, theneed for a
uniform granular structure as regardsdepth and grain size
distribution should not beneglected (e.g. grain fragmentation due
tounacceptably high consolidating energies). In thecase of cavities
under the sleepers, there arestiffness fluctuations in the ballast
bed whichresult in a concentration of stresses on somelocalised
parts in the granular structure [27].
In the shearing graph, the rise of theshearing strength is
determined by the angle offriction φ. Large angles of friction
favour the
64 RAIL INFRASTRUCTURE
Above: Figure 10: Discontinuous loadtransfer of the ballast bed
(Source: [25]).
Above: Figure 11: Rail depressions, rail foot tensions and
supporting point force with variousballast bed moduli, spring
characteristics and elastic length and a wheelset load of 100
kN(Source [23]).
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ballast bed stability and ensure good loaddistribution,
activation of large quantities ofballast and a reduction of the
strain on thesubsoil. The friction angle is determined mainlyby the
grain size distribution (irregularity,density) as well as shape,
roughness, sharpedges and edge stability of the grains. Many
ofthese parameters are not influenced by stoneprocessing and are
basically defined by rockproperties and mineralogy. To
measureadditional geometrical influencing parameters,such as
sphericity (shaped like a ball) anddegree of roundness, tests were
carried out bythe ÖBB in 2012 on all types of rock suitablefor
track ballast using the Petroscope at GrazUniversity of Technology.
For this, a quantity ofseparate stones is scanned by a laser
beamwhich enables the degree of roundness and theshape index to be
identified.
When wet, fine particles in large quantitiesact like a
lubricant, reduce the friction angleand, therefore, lower the
shearing strength.This results in unfavourable load
transferproperties and high stress peaks. They alsobind water
through capillarity action, delay thedrying out of the subsoil and
can, therefore, inthe long-term reduce the load-bearing
strengthwhich leads to settlements.
In various literature the load dispersionangle of new track
ballast in the ballast bed isstated at times with up to 45°.
Studies atInnsbruck University commissioned by the ÖBBproduced in
laboratory tests far lower values ofaround 20° (at 90% load
quantiles) for newballast. To evaluate the conditions on the
openline, tests on load dispersion were carried outon various kinds
of rock and stone shapesduring innovation measuring runs in 2012
onreal track on the new western main line Vienna-St. Pölten in the
vicinity of Tullnerfeld.
6.3. Track calculation and stress on the ballast
The stress on the ballast is normally expressedin terms of the
ballast pressure. This results fromthe load on a sleeper in
relation to the effectivesupporting surface of the sleeper in the
ballast.The greatest loads in the ballast bed, whichdestroy the
ballast stones, are primarilyquasistatic and dynamic vertical
loads.Discontinuities in the track (e.g. switch points,joint gaps)
or on the vehicle (e.g. flat spots)produce localised, dynamic force
peaks. Abruptdifferences of stiffness in the subsoil (e.g.
bridgetransitions) and non-uniform layer densities of theballast
bed react in turn on the load transfer(foundation soil-framework
interaction).
Zimmermann’s method on the basis of
considerations by Winkler [28] is applied toevaluate the stress
on the track components.Although not accepted unconditionally
indetail, Zimmermann’s method [29] producesreliable results for the
purposes of measuringand is applied at ÖBB in the form ofRegulation
B 50-Part 3 [22]. Here the rails areregarded as bearers on an
elastic foundationwith the ballast bed modulus C. The ballastbed
modulus C describes the relationshipbetween the sur face pressure
of thesupporting point and the depression and,therefore, also
contains the elasticity of theballast bed and the subsoil. The
formulae is:
PC = y
C = ballast bed modulus (N/mm3).P = surface pressure between
sleeper andballast (N/mm2).y = depression of the rail (mm).
Elastic elements such as rail pads,elastic coating on the
underside of sleepers or sub-ballast mats can be taken into
accountby superposition.
The rail deformations are dependent uponwheel load, rail
stiffness, stiffness of thesupports and sleeper spacing. As
illustrated inFigure 11, there are greater deformations onsoft
subsoil and, therefore, greater stress onthe rails. On the other
hand, hard subsoil leadsto high supporting point forces and
theassociated higher stresses on the ballast. Theuse of elastic
coatings on the underside ofsleepers and sub-ballast mats, for
example, canhelp to reduce these stresses [31].
In the ÖBB Regulation B 50-Part 3 [22],the ballast bed moduli
illustrated in Figure 12are applied. The ballast bed modulus can
bedetermined by depression measurements, railfoot tensions or
knowledge of the bendingwave at a given vertical load using the
following formulae:n From the rail foot tension:
4•E•I•a F C =A
• 4•σf•Wu (N/mm3)
n From the depression of the rail: F•a 3 F C =4•y•A
• E•I•y (N/mm3)
n From the length of the bending wavebetween the points a and b
(Figure 13):
4 4•E•I•a E•I•aL=A•C (mm) &
C= 2000•A•D4 (N/mm3)
Calculated ballast pressure under the sleeper
The basis of the calculation according toZimmermann is the
conversion depicted inFigure 14 of the cross-sleeper support
surfacein equal surface longitudinal sleepers.a = sleeper spacing.b
= width of the assumed longitudinal beam.ü = sleeper overhang.2ü =
sleeper length minus wheel contact pointdistance (1,500mm on
standard gauge,805mm on narrow gauge).A1=A2=AA1=2•ü•b1A2=b•a
2•ü•b1 A1b = a = a
The ballast pressure p under the sleeperresults from p=C•y, the
depression yaccording to the formula:
F•a y=2•A•C•L
•η
L describes the fictive sleeper lengthand produces
4 4•E•I•aL=A•C
A = half supporting sleeper surface (mm²).a = sleeper spacing
(mm).C = ballast bed modulus (N/mm³).p = surface pressure between
sleeper andballast (N/mm²).y = depression of the rail (mm).E =
modulus of elasticity of the rail steel (2.1•105 N/mm2).F =
effective wheel force (N) in compliancewith EN 15528.L = fictive
sleeper length as a basic value ofthe longitudinal sleeper track.Ix
= moment of inertia of the rail (mm4).η = Zimmermann’s influencing
factor.φ = speed factor.n = stress reversals.
The effective wheel force F is producedfrom the static wheel
force and an addition (10to 20%) for the wheel force
displacementwhen travelling through curves.
Above: Figure 12: Ballast bed modulusdepending upon type of
subsoil (Source: [22]).
Above: Figure 13: Bending line between the points a and b
(Source: [22]).
Right: Figure 14: Conversion of the cross-sleeper track in
atheoretical long-sleeper track (Source: [22]).
b1: Slanting edges andnarrowings in the middle of thesleeper
should be taken intoaccount for concrete sleepers.
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In the final part of their article, Dipl.-Ing.Christoph
Kuttelwascher, Track Expert,
ÖBB-Infrastruktur AG, Vienna, Austria, andDipl.-Ing. Michael
Zuzic, former Head of TrackDivision, ÖBB, Vienna, Austria, describe
howtrack ballast can affect the whole railinfrastructure. Literary
references (thebracketed numbers) are detailed at the end ofthe
article.
Zimmermann’s influencing factor η takesinto account the
influence of several vehicleaxles and is contained in the ÖBB
regulationB50-Part 3 in spreadsheet form. It is set at 1.0for a
single load in the middle of the sleeper.
The scatterings of the effects (quasi-static and dynamic
stresses) and resistances(ballast, cavities, subsoil) are taken
intoaccount by additions for speed and state ofrepair and
summarised in the factor s (s=n•φ). The speed factor φ is
obtainedfrom the maximum line speed and is between1 and 1.5. The
factor n lies between 0.15 and0.25 and is obtained from the line
categoryand track classification.
6.4. Resistances to lateral displacement
The resistance to lateral displacement is adecisive parameter
for measuring the stabilityof the track to buckling and depends on
alarge number of factors (sleeper geometry,contact surfaces, grain
size distribution, grainshapes, angularity, amount of ballast
aroundthe sleeper edges). It is that reaction forcethat counteracts
a displacement of the trackperpendicular to the centre line of the
track(normally after a 2mm displacement path).
The resistance to lateral displacement iscomposed of the
following resistances: n Sleeper underside friction. Resistancesat
the sleeper underside dependent on load,contact sur face and
interlocking and/orcoefficient of friction. According to [24]
adistinction is made between primary andsecondary sleeper underside
resistance.n Shoulder resistance. Active soil pressure
as per soil pressure theory dependent oncoefficient of friction,
height of layer andmaterial characteristics.n Sleeper-end
resistance. Passive soilpressure as per soil pressure theory
becomeseffective only from a certain movement.
After ballast bed cleaning or tamping, theresistances to lateral
displacement arereduced by between 40 and 50%. Thedynamic track
stabilisation increases theresistance to lateral displacement by
between30 and 40% [23]. The percentages of the partresistances
given in trade literature fluctuatedepending upon the measuring
method used.However, all in all, approximately half of thetotal
resistance to lateral displacement isdetermined by sleeper
underside friction andon elastic-coated sleepers up to around
60%.
To establish the influence of differenttypes of ballast (granite
and dunite), elasticcoatings and safety caps on the resistance
to
lateral displacement, tests werecommissioned by ÖBB in 2010 and
carriedout by Munich University of Technology usingthe
single-sleeper method and have beenpublished in [24].
To perform the measurements a skeletontrack with two uncoated K1
pre-tensionedconcrete sleepers was set up in the test rig.The depth
of the ballast bed was 45cm whichis equivalent to a ballast depth
of 23cm belowthe lower edge of the sleeper. Sub-ballastmats of
varying stiffness (Cstat = 0.045N/mm³ and 0.28 N/mm³) were used
tosimulate the subsoil. Ballast bedconsolidation was performed
using a vibratingplate and a manual packing device. The testset-up
can be seen in Figure 15.
Depression, stiffness, ballast bed modulus
The depressions under static and dynamicload were measured using
inductivetransducers. After a simulation of three millionload
alternations with an upper load of 225 kN, the static and dynamic
ballast bedmoduli, the settlement behaviour and theresistance to
lateral displacement of theindividual sleepers were
established.
When the consolidation condition isreached after around 250,000
loadalternations, the oscillation amplitude (declineof elastic
deformations) drops, whereas theplastic deformations continue to
increase.
With the same grading curve the duniteshowed during the fatigue
level test,compared to granite, a lower static anddynamic stiffness
combined with greaterplastic deformations. After three million
loadalternations the plastic deformation of thegranite ballast on
stiff subsoil (Cstat = 0.28N/mm³) was around 6mm, whereas that
ofthe dunite was around 9mm. After a load of 3million load
alternations the static ballast bedmodulus was on average around
0.155N/mm³ and the dynamic ballast bed moduluswas around 0.195
N/mm³.
For the test the sleeper-end ballastwas 0.50m horizontal and the
adjoining
Track ballast in Austria: Part 3.
RAIL INFRASTRUCTURE 63
Above: Figure 15: Test rig during the fatigue level test.
(Source: ÖBB).
Above: Figure 16: Resistance to lateral displacement graph of a
single sleeper measurementwith safety caps. (Source: ÖBB).
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embankment slope was 1:1.5. After theentire loading cycle the
rails were
uncoupled from the sleepers to measure theresistances to lateral
displacement. Then, theindividual sleepers were displaced crosswise
tothe centre line of the track, without a verticalload. The
horizontal load was commenced in theneutral axis of the sleeper,
the force occurring atthe 2mm deformation path (transition
staticfriction - sliding friction) was taken as a rulingresistance
force. The calculation was madethrough the relation to the sleeper
spacing of600mm in the unit N/mm.
Figure 16 shows a typical force-deformation curve of a
resistance to lateraldisplacement measurement with safety caps.
Figure 17 shows with dunite ballast onsoft subsoil a lateral
resistance increased by27% (compared to hard subsoil), which is
dueto a higher density through the largeroscillation amplitude and
greater plasticdeformation due to the rearrangementprocesses. On
hard subsoil, the resistance tolateral displacement to granite
ballast isslightly reduced due to the lower stability ofthe
edges.
Due to temperature expansions, highforces act to the outer side
of the curve,especially in very tight curves, which
withoutadditional measures would produceunacceptably high
deformations. Here safetycaps are applied as a means to increase
theresistance to lateral displacement. Theresistances to lateral
displacement were alsomeasured with safety caps installed in
orderto check their effectiveness. Here theincrease of the
resistance to lateraldisplacement was on average around 30%(Figures
16 and 17). With ballast bed depthsover 45cm a further increase can
be expecteddue to the additionally activated pressurecone
downwards.
7. Reduction of the mechanical track ballast loadsUniform
consolidation and homogeneity of theballast bed are important
requirements toreduce the loads on the ballast
structure.Immediately after mechanised ballast bedcleaning and
tamping, the ballast is onlycompacted in the influencing zone of
thetamping tines. A homogeneous consolidationin the entire
cross-section is aimed at throughthe application of dynamic track
stabilisation.Irregular settlements due to traffic loads arereduced
and anticipated in a uniform way,increasing the resistance to
longitudinal andlateral displacements and reducing cavitiesunder
the sleepers. The dynamic trackstabilizer exerts a vertical load on
the trackand places it in horizontal oscillations of 30-37 Hz. Due
to the low ballast pressure ofapproximately 8 N/cm², this is also
referredto as ‘force-free spatial consolidation’ [31].
Another course of action to extend theservice life of the
ballast bed is the specificapplication of elastic elements such as
elasticcoating on the undersides of sleepers and sub-ballast mats.
The resulting lower mechanical
stresses on the ballast stones result from themore uniform
support conditions on the onehand and from a dampening of the
dynamicpulses from the traffic loads on the other. Dueto the use of
elastic undercoating, the contactsurfaces between sleeper and
ballast can bemultiplied [24].
An increase of the contact surfaces isalso obtained through
modified sleeperdimensioning, for example frame sleepers(Figure 18)
or HD sleepers.
8. OutlookThe quality of the track ballast used in the
linenetwork of Austrian Federal Railways isregulated by the
‘Production and Supply ofTrack Ballast’ and by the technical
conditionsof delivery for track ballast (BH 700). TheEuropean
standard EN 13450 serves as abasis for the requirements.
All suppliers of railway ballast must haveCE conformity
certification and pursue acertified, regular, internal production
controlsystem. Typically, the quality is guaranteed by initial
testing, conformity testing andidentity testing.
In the EN 13450, the Los Angeles testingmethod has been laid
down as a Europeanreference method to determine the resistanceof
track ballast to fragmentation. The foundationwas tests carried out
by the European RailResearch Institute (ERRI) in 1991 and
1992.Practical experience shows that a singlereferencing on the Los
Angeles coefficient (LAvalue) does not completely reflect
theexperience of the Austrian rail network.Therefore, Austrian
Federal Railways also usesthe impact fragmentation coefficient and
theMicro-Deval coefficient as additional qualitycriteria. In
addition, over past years, alternativetesting methods have been
investigated, further
developed and in some cases published [19].Some of these testing
methods are suitable forroutine application and may lead to
furtherdevelopment in this sector.
In order to correctly evaluate the behaviourof the Austrian
track ballast in the rail networkof Austrian Federal Railways, and
to drawconclusions about quality figures, a greatnumber of
investigations were carried out in theÖBB rail network in the years
2010 to 2012 inthe course of a project on the systematicobservation
of the subject of track ballast.Taking into account the framework
conditionssuch as track components, drainage, subsoilstiffness,
etc, ballast samples were taken andmaterial tests were performed by
accreditedtest institutes and universities.
It is evident that only a systematic view (intechnical,
organisational and commercial terms)will be effective. For example,
modifications oftechnical requirements automatically haveeffects on
supplier structure, transport costsand worksite logistics. On a
technical basis allcomponents of the track must be compatible. Asa
part of this system, the track ballast usedplays an important role.
When there isinsufficient drainage, poor subsoil or dynamicstresses
due to discontinuities in the trackstructure, even the highest
quality track ballastcannot compensate for the deficiencies in
theoverall system.
An important commercial difference oftrack ballast to other
track components is that the transport costs make up a
highproportion of the overall costs for supplyingballast to the
worksite. The requirement ofmaximum track ballast quality at a low
price,with the best possible assurance of supplyand minimum
transport distances, shows thenecessity of regarding the subject of
trackballast systematically.
Right: Figure 17: Calculated resistances tolateral displacement
of individual sleepersafter the fatigue level test with three
millionload alternations. (Source: ÖBB).
Right: Figure 18: Visible ballast stone contactsurfaces of an
elastic-coated frame sleeper inthe St. Pölten area. (Source:
ÖBB).
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RAIL INFRASTRUCTURE 65
Literary references[1] Klotzinger, E. (2008): Track ballast.
Part1: Requirements and stress. In: ETR, 01-02/2008.[2] Klotzinger,
E. (2008): Track ballast. Part2: How quality develops over time
andthresholds for action In: ETR, 03/2008.[3] Issler, L./Ruoß,
H./Häfele, P. (2003): Science of material strength
-Fundamentals.[4] Dietrich, H. (1994): Mechanical Testing of
Materials: Foundations, TestingMethods, Applications.[5] Anthes, G.
(2006): Study Fundamentalinquir y into deposits of granite stone in
Austria.[6] http://www.volcanodiscover
y.com/de/vulkane/lexikon/basalt.html[7] http://www.wikipedia.org[8]
Technical conditions of delivery for trackballast BH 700; ÖBB
Infrastructure AG,1. Aug. 2007.[9] ÖNORM EN 13450 Aggregates for
trackballast; Austrian Standards Institute in theapplicable
version.[10] ÖBB Infrastruktur AG (March 2011):Testing system as
per Ar ticle 53 RL2004/17/EG in the applicable versionconcerning
the ‘production and supply of trackballast of particle size I and
II’.[11] ÖNORM EN 933-4 Tests for geometricalproper ties of
aggregates, Par t 4:Determination of particle shape - Shapeindex.
Austrian Standards Institute in theapplicable version.[12] ÖNORM EN
1097-2 Tests for mechanicaland physical properties of aggregates.
Part 2:Methods for determination of resistance to
fragmentation. Austrian Standards Institute inthe applicable
version.[13] ÖNORM EN 1097-1 Tests for mechanical and physical
proper ties ofaggregates. Par t 1: Methods fordetermination of
resistance to wear (Micro-Deval). Austrian Standards Institute in
theapplicable version.[14] ÖNORM EN 1097-6 Tests for mechanicaland
physical properties of aggregates. Part 6:Determination of particle
density and waterabsorption. Austrian Standards Institute in
theapplicable version.[15] ÖNORM EN 1367-1 Tests for thermaland
weathering properties of aggregates. Part1: Determination of
resistance to freezingand thawing. Austrian Standards Institute
inthe applicable version.[16] ÖNORM EN 1367-2 Tests for thermaland
weathering properties of aggregates. Part2: Magnesium sulphate
test. AustrianStandards Institute in the applicable version.[17]
Austrian standard EN 1367-3 Tests forthermal and weathering proper
ties ofaggregates. Part 3: Boiling test for sunburnedbasalt.
Austrian Standards Institute in theapplicable version.[18] ORE
(1991): Uniform assessmentcriteria of ballast quality and
evaluationmethods of ballast condition in the track.Question D 128.
Report No. 2.[19] Bach, H./Kuttelwascher, C./Latal, C.(2012):
Alternative testing methods for qualityassurance of track ballast.
In: ZEVrail,3/2012.[20] Swiss Association of Road and
TrafficSpecialists (February 2008): SN 670 830bTest procedure for
mechanical and physical
proper ties of aggregates - method for determining the
compressive strength oftrack ballast.[21] Breymann, H. (2011):
Mechanicalcriteria for the track ballast - point load
test,fragmentation. Repor t to the ÖBB(unpublished).[22] B 50-Teil
3 (März 2012): Permanent waycalculation. ÖBB Infrastruktur AG.[23]
Lichtberger, B. (2003): TrackCompendium.[24] Iliev, D. (2012): The
horizontal trackgeometry stability of the ballasted track
withconventional and elastic coated sleepers. In:Munich University
of Technology, RoadConstruction Department and Testing
Office,Publications: Brochure 86.[25] Fröhlich, O. K. (1934):
Pressuredistribution in the foundation soil.[26] Kruse, H. (2002):
Model-assistedinvestigations of track dynamics and thebehaviour of
railway ballast. Dissertationsubmitted to Hanover University.[27]
Holtzendorff, K. (2003): Investigationinto the settlement behaviour
of railwayballast and the development of cavities onballasted
tracks; Dissertation submitted toBerlin University of
Technology.[28] Winkler, E. (1867): The science ofelasticity and
stability. [29] Zimmermann, H. (1941): Calculation ofrailway
permanent way. [30] Auer, F./Schilder, R. (2009): Technicaland
commercial aspects on the topic of soledsleepers - Part 1:
long-term experience in theÖBB network. In: ZEVrail. April
2009.[31] Lichtberger, B. (2007): The LateralResistance of the
Track. In: EIK 2007.