Railway Ballast Requirements for High Speed and Heavy Haul Lines:

7/23/2019 Railway Ballast Requirements for High Speed and Heavy Haul Lines:

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Railway Ballast Requirements for High Speed and Heavy Haul Lines:

Hardness, Fouling, Life CycleGiannakos KonstantinosCivil Engineer PhD, F. ASCE, M. TRB-AR050&AR060, AREMA, fib.,

Visiting Professor of Railways, Dpt. Civil Engineering, University of Thessaly, Greece

Loizos AndreasCivil Engineer, PhD, Professor,Department of Transportation Planning and Engineering,NTUA, Greece

Plati Christina

Civil Engineer PhD, Laboratory of Highway Engineering, NTUA, Greece

1 INTRODUCTION

During the study for the dimensioning as well as

the selection of the individual materials of a railway

track, the weak links are the ballast and the sub-

structure. These elements of the track present resid-

ual deformations as a percentage of the deflec-tion/subsidence, directly connected to the

deterioration of the so-called geometry of the track,

which can be nevertheless described much more

specifically as quality of the track. The smaller the

residual deformations and the slower their alteration

over time, the better the quality of the track. A rail-

way track is a multi-layered structure (Fig. 1) con-

sisting of a vertical succession of various materials

or layers of materials that define the final position of

the rail running table as well as the properties of the

track itself, as it reacts to the action that is cre-ated from the motion of the railway vehicle. Each

material or layer that constitutes the line can be

simulated by a combination of a spring with spring

constant kiand a damper with damping coefficient

ci.

According to the theoretical analysis of Winkler,

Timoshenko, and others (e.g. Zimmermann), that

model the track as an infinite beam on an elastic

foundation, the deflection of the track should be high

enough to distribute the acting load to a longer sec-

tion of the track and thus to reduce the reacting forceat each point. This amount of deflection can be

provided by a resilient fastening and its rail pad,

since the substructure should be constructed to be as

undeflected as possible in order to prevent or to

minimize permanent vertical deformations. This

function of the ballast-bed in every railway track

implies its deterioration and the subsequent fouling

of ballast that leads to costly maintenance works.

The authors have been involved in research

programs of the National Technical University ofAthens (NTUA) for the Hellenic Railways

Organization (OSE) to develop modern Technical

Specifications for ballast. In the present paper a

portion of the investigation is presented.

ABSTRACT: Results from tests performed on ballast used in the Greek network, as well as a new method for

the estimation of ballast fouling as a function of ballast hardness are presented in the present paper. Stresses

that develop under the seating surface of the sleeper and that are transmitted to the ballast, influence mainte-

nance intervals and cost. Ballast hardness influences the fouling and consequently the life-cycle of the mate-

rial laid at the ballast-bed. This leads to the determination of a minimum quality for the technical specifica-

tions in relation to traffic conditions (daily tonnage). The present paper discusses these issues and results from

the research programs performed on the Greek railway network.

Figure 1 Typical simulation of ballasted track as multi-layeredstructure / combination of springs and dampers, with character-istic values of spring constants i (static stiffness coefficientin kN/mm) per layer

2 BALLAST PROPERTIES REQUIREMENTS

2.1 General

In Greece a High Speed Line of mixed traffic

(maximum operational speed V250 km/h and axle

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load 22.5 t) on the main corridor Patras - Athens -

Thessaloniki - Eidomeni (frontier with FYROM) is

under construction with the funding of European

Union and Greek Government. Until 1999, only

twin-block concrete sleepers were used, which were

of French technology, type Vagneux U2, U3 with

RN fastenings and U31 with Nabla fastenings. Nabla

fastenings are laid also in the TGV (High Speed

Trains) lines in France. After almost 12 years of op-eration extended cracking on sleepers U2/U3 and

completely fouled ballast-bed were observed. A

twenty-year research program to determine the

causes was initiated to study the sleeper -ballast

system under the specific conditions (rolling stock,

ballast quality, rail running table, level of mainte-

nance, etc.). The research program (in which one of

the authors, Dr K. Giannakos, participated as head of

the Hellenic railway scientific team and co-ordinator

of the research and the other two as members of the

research team) was conducted by OSE Hellenic

Railways Organization with the participation of

European universities and research centres of rail-

way organizations. It included both laboratory tests

and investigation of the phenomena that occurred on

the track. After the end of the first part of the inves-

tigation program, a part of which was for the ballast,

the requirements for ballast properties were changed

in the Greek network.

2.2 Ballast requirements for High Speed Lines

and Greek regulationsBallast material should be produced from solid

rocks with angular grains. Its durability should

secure drainage of rain water, absorb vibrations as

damper and provide the best conditions for

maintaining the geometry of the track after tamping.

Selig & Waters (1994/2000), describe the properties

that ballast should fulfill. Due to these demands

ballast grains should provide both the relevant

strength for:

(a) the Deval Wet attrition test, (Selig & Waters,

1994/2000, and SNCF, 1985 and modifications), re-

placed more recently by microDeval attrition test.

The Deval test characterizes the ballast resistance in

the abrasive degradation between the ballast grains,

particularly in the area between the sleepers (see

relevantly Giannakos, 2004) and

(b) the Los Angeles Abrasion test, (Selig & Wa-

ters, 1994/2000, and SNCF, 1985 and modifica-

tions), that characterizes the value of the ballast

strength in impact loading (shock).

Experience from French network in both conven-tional lines (maximum operational speed up to 200

km/h) and High Speed lines (maximum operational

speed up to 300 km/h) and the experience from the

Greek network (maximum operational speed up to

160/170 km/h) show that the combination of the re-

sults of the aforementioned two tests give the speci-

fication for the total ballast strength. These two tests

lead to a coefficient of total hardness of ballast, as

derived from a double entry diagram (see Gianna-

kos, 2010b) cited in both French and Greek regula-

tions, and adopted after the common research pro-

gram (Giannakos, 2004). This coefficient depicts the

ballast behavior with the time passing. The DevalWet attrition Coefficient (D.H.) is entered on the

horizontal axis and the Los Angeles Abrasion

Coefficient (L.A.) is entered on the vertical axis. The

intersection point of the two parallel lines to the axes

drawn from D.H. and L.A. is located between two

consecutive trapezoidal lines so the coefficient of

instant hardness of ballast DRi, and the coefficient of

total hardness of ballast DRGis calculated as the

average of twelve samples (twelve DRi). The

relative quantity of powder, created by impact

stressing and abrasion, is proportional to the

coefficient of total hardness (DRGaccording to

regulations). This coefficient provides the "meas-

ure" of life-cycle of the ballast laid on track (Loizos

et al., 1992-1993).

2.3 Greek Standards for Ballast

Figure 2 Definition of Railway Ballast Hardness DRiaccordingto the Greek and French Regulations through Los Angeles co-efficient (LA) on the vertical axis and Deval Wet (humide) co-efficient (DH) on the horizontal axis. DRiis defined at the in-tersection of the two lines of LA and DS parallel to the axis-and the area among the trapezoidal scale (from 5 to 32).

The Ballast Hardness DRi is defined, accordingthe Greek and French Regulations before the enact-ment of the European Standards for railway ballast,through the Los Angeles coefficient and the Deval


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coefficient, via a diagram of double input (Fig. 2) inaccordance to French railways' regulation. The hard-ness of ballast was investigated in the past also inGreece in relation to the concrete ties (Loizos et al.,1992-1993).

Ballast hardness was measured in laboratory ac-cording to: (a) Los Angeles (L.A.) test per ASTMC131, (b) L.A. test per the French Normes NFP

18573, (c) Deval test and (d) the total hardness DRiderived from the combination of L.A. (French) andDeval tests (French and Greek regulations).

2.4 European Standards (E.N.) for Ballastrequirements

Recently, the European Committee for Standardi-zation published the European Standard for RailwayBallast (EN 13450, 2002), applicable in all MemberStates of E.U., and the relevant Greek OrganizationELOT, adopted it with the publication of the Greek

Standard (ELOT 13450, 2003). The EuropeanStandards, as most of the E.U. directives, are derivedas a compromise among the national regulations ofthe Member States, and as such the EN 13450 onlytakes into account the L.A. coefficient. It should benoted that the non-uniformity of support with swing-ing sleepers (Hay, 1982) is unacceptable for goodtracks. In High Speed lines as well as in conven-tional lines the track must be of excellent quality andconsequently situation of a non well seated track -with voids under the sleeper seating surface and

swinging sleepers, permitting abrasion among theballast grains and the sleeper- is "forbidden". Afterthe enforcement of EN 13450 there was a need offinding the correspondence between the older andnewer regulations as well as the correlation between

ballast hardness and ballast life-cycle on track, ac-cording to existing literature from older tests andmeasurements. For this purpose an investigation

program was undertaken (Loizos et al., 2006-2007).

2.5 Heavy Haul Railways

There is a general discussion in railway engineer-

ing cycles and academics that in Heavy Haul rail-roads (wheel loads 17.69 t or 39,000 lb and maxi-mum speed 60 mph or 96,6 km/h) the actions/loads

per sleeper are higher than in the High Speed linesof mixed traffic (wheel loads 11.25 t or 24,800 lband V 250 km/h or 155.34 mph). This discussioncould lead to the false conclusion that Heavy Haulgenerates much more severe actions on sleepers, bal-last and substructure. It has to be underlined that alltheoretical methods in international literature are

based on exactly the same theoretical approach

based on Winkler's theory also adopted byZimmermann. According to Eisenmann (1984) thetheoretical calculation gives results close to the av-erage of the measurements on track under operation.In the present paper an analysis is presented accord-

ing to the methods cited in the American literatureand Giannakos (2004) method. Finally a comparison

between the loads on track imposed by Heavy-Haultraffic with slow speeds and High Speed traffic withnormal axle loads and 300km/h or 186.45mph yieldsresults more adverse for the case of High Speedlines, in many cases (see also a more detailed analy-sis in a forthcoming TRR 2011 issue, (Giannakos,

2011).

3 BALLAST-BED STRESS ANDDEFORMATION

3.1 General

For a given quality of ballast material, as far as

the part of the deformations caused by the ballast

and the earthworks of the track are concerned, the

correct combination and usage of heavy track ma-

chinery is planned for the accomplishment of the

geometry of the track according to the level pre-scribed in the regulations. In modern railway track

construction, on High Speed lines, for the layers un-

derneath the ballast a very well-executed construc-

tion is required: crushed stone material in the upper

layer, 100% Modified Proctor or 105 % Proctor

compaction. This specification implies a substruc-

ture almost undeflected (with minimal contribution

of the subgrade to the total deflection) scoping to the

diminishing of the permanent deformations, since

residual deformations are a percentage of the actual

deflection of the railway track caused by the passing

of the loads (Hay, 1982) and they originate mainly

from the substructure and ballast. This leads to an

almost proportional deterioration of the geometry of

the track. This means that the deflections should be

kept, if possible, almost zero. However, the need of

significant deflection development, in practice, in

order to achieve a distribution of the acting load to

the adjacent sleepers contradicts the requirement to

minimize track deflection. This significant deflec-

tion should be offered by the fastening and its railpad (Giannakos, 2011). As for the issue of ballast

fatigue, the existing literature assumes a uniform

distribution of stresses under the sleeper and without

further details uses the mean value of stress on the

ballast-bed.

But in reality, the seating of the sleepers is sup-

ported on discrete points, points of contact with the

grains of the ballast as well as points of contact

among the grains of ballast, (Fig. 3) and the resulting

necessity to calculate the stress per grain of ballast

cannot give comparative results to the rest of the lit-erature. So it is possible to use the mean value of

pressure not as an absolute quantity, but compara-

tively and in combination with the possibility it cov-

ers. Dr. J. Eisenmann, (1988) also shares this view

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stating that the mean value of pressure is a criterionfor the stressing of the ballast on track.

Figure 3: Ballast grains in the ballast bed and transmission of

stresses and actions.

There is no uniform support of the sleeper on the

ballast, nor uniform compaction of the ballast and

the ground and there are faults on the rail running

table, imperfections on the wheels etc. A decisivecoefficient in determining the dimensioning of the

superstructure is the maximum value which is cal-

culated, based on probability laws, from the mean

value and standard deviation. In order to calculate

the value of the load that stresses the sleeper, the tri-

ple value of the standard deviation (Giannakos &

Loizos, (2009)) is taken (probability of occurrence P

= 99.7%) and for the ballast twice the value of the

standard deviation, of the dynamic component of the

load (probability of occurrence P = 95.5%).

3.2 AREMA method

In AREMA (2005) the following equation is

given for the mean value of stress p ballaston ballast-bed:

4

(1)

Where: Qwheel= Static Wheel Load, Qtotal = TotalWheel Load static and dynamic, Lsleeper = length of

the sleeper i.e. 8-6 or 2590 mm, e = gauge of the

track (~1500 mm), Leff-sleeper effective length of the

sleeper, bsleeper= width of the sleeper at the seating

surface, IF = impact factor

(2)

Where: the distance between the sleepers, total=

total static stiffness coefficient of the track, E,I themodulus of elasticity and the moment of inertia of

the rail.

3.3 Giannakos (2004) method

The mean stress on the upper surface of forma-

tion (ballast) can be calculated by the following

equations:

(3)

(4)

(5)

Where: Ab= the sleeper seating surface (for

monoblock sleepers the central non-loaded area

should be subtracted), Q=Component of the load

due to cant deficiency, (QNSM) standard deviationof the dynamic component of the load due to Non-

Suspended Masses, (QSM) standard deviation ofthe dynamic component of the load due to Sus-

pended Masses (Giannakos, 2010 a).

It must be noted that even French and German lit-

erature cites that the measurements on track indicate

that the dispersion of results due to the dynamic

loading should be taken into consideration, entering

the calculation through coefficients depending on

the probability of the occurrence of various parame-

ters (Eisenmann, 1980, Eisenmann, 1988). A

smaller coefficient of probability of occurrence(95.5% with t=2 or even 68.3% with t=1) is used for

the formation of the track (Eisenmann, 1988).

2 2

NSM SM

subsidence wheel

Q Q

RELATION BETWEEN BALLAST LIFE-CYCLE AND FOULING

4.1 Ballast Fouling as a function of BallastHardness

The ballast-bed acts as a damper to the loads ap-

plied on the track through the friction between itsgrains and of its resilience. In order to maintain

these properties the voids of its structure should

not be filled either by up-moving soil (pumping) or

by the small particles or powder created by the attri-

tion induced from loading. When the voids between

the grains of the ballast-bed are filled beyond a cer-

tain point, commonly referred to as fouling, a well-

compacted and polluted ballast-bed is created that

loses its resilience and it cannot be tamped or main-

tained. Moreover, it forms an undeflected seating,

increasing the actions undertaken by the track andreducing the possibilities of well-performed tamp-

ing. In this case the track geometry is not main-

tained. For these reasons it is very important to find

1100

wheel stat

total stat ballast

eff tie tie tie tie

Q AQ A

pL b L e

IF

b

totalA3

TR

p A Qh

Q C

2

total

b

C

A

3

3

TR

AE

41

2 2

subsidence J h

statE

41

2 2


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a relationship between the ballast quality and the

life-cycle of ballast on track and assess the impact of

ballast fouling.During a research program from 1988-2008, The

Hellenic Railways Organization investigated thematter of ballast quality and life-cycle. The authors

of the present paper participated, over a long period

of time either in collaboration or separately in this

investigation program.During the investigation performed at the French

Railways (SNCF) laboratories, tests on the Greek

and French ballast were executed. Cyclic load testresults for hard limestone ballast, as well as for

metamorphic, eruptive and magmatic ballast per-formed in the Vibrogir device (the device is de-

scribed thoroughly in Giannakos, 2010 b) already

existed at the SNCF (e.g. Lecocq, 1988). The ex-periments, as scheduled and performed, simulate a

track under real conditions with a circulation of 22.5tons per axle and over 200 km/h speed. For the

ballast fouling the number of cycles simulates the

number of tonnage passing over the track. This testis scheduled and approved in the French State Rail-

ways (for speeds V>300km/h). Tamping influence isnot measured in this test. A ballast hardness of

DRG=12.2 was used as an average for the Greek bal-

last and DRG=16.3, 19.2, and 21 for the French bal-last (metamorphic, eruptive and magmatic). For the

ballast material box test have also performed and

their results are described in Giannakos, (2010 c).The following equation was derived from laboratory

test results and can be used to calculate the lowervalues of hardness (Giannakos, 2010 b):

(6)

Figure 4 Relation between the Los Angeles coefficient accord-ing to French regulations (LA-Fr) and the Los Angeles coeffi-cient according to English regulations (LA-En).

where: percentage = the percentage of fines in a

determined area under the sleeper's seating surface

constituting the polluted area of ballast-bed.According to the measurements performed at the

laboratory of the SNCF and the experience inFrance, when the percentage of fines is >12.5%, the

case where the ballast is considered to be completely

fouled (no sufficient tamping work can be per-

formed) and needs replacement or cleaning or risingof the track of at least 15 cm or approximately 6

inches, t = hours of operation of Vibrogir test,

DRG/DRi =the global or instant hardness of ballast

according to the French (and Greek) regulations forrailway ballast derived from the coefficients Los

Angeles and Deval Wet as shown below, which

is extracted from the Greek ballast regulations. It isobvious that the fouling due to ballast's wear is dif-

ferent from the case of coal dust ballast fouling(Tutmuluer et al., 2008). The increase of the fines

and the reduction of void spaces lead to a more

compacted ballast reducing its operation as damperand worsening its capability to keep in high level its

"maintenability". The coefficient is determined bythe following equations:

(7)

This equation fits the experimental results for

U41 twin-block sleepers of the French Railways laidand in TGV lines with a maximum speed 300 km/h

and is applicable for all conditions (different type ofsleepers and fastenings and different ballast quality).

Although it is not a linear relation it could be ap-

proximated as such (see relevantly Selig & Waters,1994/2000). A test of 100 h in the Vibrogir device

is equivalent to a circulation/passing of 360,000,000t or 396.9 billion lb, which is equivalent to the fa-

tigue that a track panel undergoes during a period of

12 years with a traffic of 120,000 t/day or 132.3 mil-lion lb/day, corresponding to the limit Tf2between

the groups of traffic UIC 1 and 2 according to thecode 714 R of the International Union of Railways

(UIC, (1989)). For more details about hours in Vi-

brogir and the test the interested reader should read(Giannakos, 2010 b).

0 36

6 4 28

0 745 16 3

2 10 16 3

.

.

. .

.

G G

G G

DR for DR and

DR for DR

4.2 Correlation between French and Englishcoefficients for Los Angeles and Deval

The Hellenic Railways Organization (OSE)

applied the new European Standard (E.N. 13450) for

railway ballast. For this purpose, the N.T.U.A. per-formed a research program (Loizos et al., 2006-

2007) to contribute to the determination of a relationbetween the EN and the French regulations for bal-

2DR

110

0 810G

G

percentage tDR

.

LA(EN) = 0,761 LA(FR) - 0,004

R2 = 0,92

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

0.00 5.00 10.00 15.00 20.00 25.00 30.00 35.00 40.00 45.00

LosAngeles(EN)

Los Angeles (FR)

5


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last, in order to establish a relation between ballasthardness and life-cycle as derived from past tests

(Giannakos, 2010 b).The correlation between Los Angeles coefficient

according to French regulations methodologyLA(Fr) and the Los Angeles coefficient according

to English regulations methodology LA(En) is

given by the Eq. (8):

( ) 0.761 ( ) 0.004LA En LA Fr

( ) 0.889 ( ) 16.668MD En DE Fr

(8)

This correlation (Loizos et al., 2006) is depictedin Fig. 4 as derived from the N.T.U.A. laboratory

measurements.The relation between the Deval dry coefficient

according to French regulations methodology

DE(Fr) and the Micro-Deval coefficient accordingto English regulations methodology MD(En) is

given by:

(9)

This relation (Loizos et al., 2006-2007, (14)) isdepicted in Fig. 5 as derived from the NTUA labora-tory measurements.

These two equations (8) and (9) permit the corre-lation between the ballast quality of the old Greek(and French) technical specification determining thehardness DRiand the ballast quality of the newtechnical specification for railway ballast accordingto the European Standard EN 13450. These equa-tions permit the use of the above relations predictingthe life-cycle of ballast on track in relation to thehardness DRi.

Figure 5 Relation between the Deval dry coefficient accordingto French regulations DE(Fr) and the Micro-Deval coefficientaccording to English regulations MD(En).

4.3 New classification of railway ballast accordingto E.N. 13450 and correlation to DRi

According to the Greek new technical specifica-tion for railway ballast, in conformity with EN

13450, the following classification is valid as de-

picted in Table1 with the relevant correlation to thehardness DRi:

5 RELATION BETWEEN BALLASTQUALITY AND LIFE CYCLE

Due to the fact that concrete sleeper types have

different surfaces, the above relations and the fol-lowing equation are combined (Giannakos, 2010 b):

t F

t F

3

1 14

2 2

(10)

where: ti = hours in Vibrogir for two different

types of sleepers, Fi = the seating surface of thesleeper.

Combining equations (6), (7) and (10) yields theresults presented in Table 2. The table presents the

ballast life-cycle as a function of ballast hardnessand sleeper seating surface and can be used for every

ballast quality (e.g. for eruptive as well as for lime-

stone ballast) and/or concrete sleeper type. The re-sults of Table 2, for the case of U31 twin-block con-

crete sleeper (187,200 mm2), can be verified in

practice on the Greek Railway network for ballast

maintenance (renewal of the ballast bed or track ele-vation by adding 15 cm of new layer of ballast on

the top of the existing).

The results of Table 2 lead to a decision ofadopting as minimum hardness for high speed lines

network ,class K1, or DRi=16, as in the Greek

Railways also happened.

6 CONCLUSIONS

Conditions for the Greek railway network and theresearch programs performed led to relations

between the ballast hardness and the fouling of the

TABLE1:

Classification of Railway bal-last according to EN 13450

New Specification Old SpecificationK1 DRi 16K2 DRi 14K3 DR 12iK4 DR 8iK5 LA=35K6 LA=40

TABLE 2 Years of Ballast Life-Cycle on Tracks

Daily Tonnage

of the Line

30.000t 40.000t

ConcreteSleeper typeTwin-block

Seating

Surface187,200

mm2

Seating

Surface243,600

mm2

Seating

Surface187,200

mm2

Seating

Surface243,600

mm2

DRi 8 5 6 4 5

DRi 12 18 21 13 16

DRi 14 28 33 21 25

DRi 16 42 49 31 37

MDE(EN) = -0,889 DE(FR) + 16,668

R2 = 0,61

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00

Micro-Deval(EN)

Deval (FR)


7/77

iviles.

ballast-bed, at the limit of either the replacement of

the ballast or the elevation of the track, that is the

life-cycle of the material in the ballast-bed underdetermined conditions of traffic and passing

tonnage. The relations lead to the determination of aminimal quality of ballast material for the

requirements of a railway network. In this paper this

case was presented mainly in relation to High Speed

-but also to Heavy Haul-railways as far as thedegradation of ballast both in shock and abrasive

wear is concerned.

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ELOT 13450, Greek Standard, Aggregates for Railway Bal-last, Athens, Greece, 2003.

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Documents

Railway Ballast Requirements for High Speed and Heavy Haul Lines: