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Railway Track Science &

Engineering

Ballast: Issues and Challenges

International Workshops

Decision process

for ballast cleaning

and/or renewal at

INFRABEL

Paul Godart

Chief Civil Engineer

Paris 05-06 december 2013

Map of Belgian network

05-06.12.2013 Ballast: Issues and Challenges International Workshops 2

1. Network specifications

Infrastructure - Some Figures ( 2012)

• Length of main tracks : 6468 km

• Length of lines : 3600 km

• High speed tracks (300 km/h) : 273 km

• Length of secondary tracks: 2 506 km

• Turnouts : 4 470

• Level crossings: 1 857

• Bridges : 4 527 Tunnels : 177

• Global cost for track

• maintenance and renewal :

277 013 687 €


1. Network specifications

Ballast : some

figures

• According to UIC figures : in 2010 : 1 020 953 km railway lines in

the world ;

• More than 95 % are ballasted tracks : ballastless track is in

development but remains limited ( high speed lines, …) ;

• 1 km of plain track : 3 000 to 4 000 T/ballast;

• 1 T ballast : between 8 to 12 €/T ex quarry;

• Transportation costs : from 0,1 €/T/km for a direct train to 0,45

€/T.km for a single wagon; 0,20 €/T.km by truck;

• 1 km ballast renewal : between 120 000 and 180 000 €/km. 4 05-06.12.2013 Ballast: Issues and Challenges International Workshops

Ballast functions

• Distribute vertical loads from sleepers to subgrade

• Lateral and longitudinal resistance of the track ( continuous welded rails, braking, acceleration)

• Drainage

• Attenuate train vibrations, noise absorption

• Mechanical maintenance : restore track geometry with tamping machines


2. Ballast specifications

Q

Typical cross section of double track



Ton of ballast for a double track : approximately 6 to 7 tons/m

Subgrade

Monobloc sleeper Bi-bloc sleeper

Blanket layer

Geotextile

Drainage tube

Drainage material

Foundation layer

Footpath

Footpath material Channel

Concrete

Rail

Natural ditch

Catenary pool

Subsoil

Ballast

Ballast

classification

Four quality classes for ballast :

• Class IA : - very hard stones and with high cleanliness

- for speed > 220 km/h

- for speed > 160 km/h (with blanket layer)

- in tunnels

• Class IB : - very hard stones for the most important lines

- for speed ≥ 140 km/h

• Class II : - hard stones for other lines

• Class III : - stones for secondary tracks



Ballast Specifications

The ballast must meet several criteria based on European

standard EN 13450:2013 ( revised version of first standard 2002) :

• Particle size distribution

• Flakiness index

• Shape index

• Cleanliness

• Assessment of fines

• Mechanical and physical properties :

- resistance to fragmentation ( Los Angeles)

- resistance to wear (micro Deval)



Ballast renewal :

life cycle

• Why is it necessary to

clean and/or relay

the ballast ?

After how many years?

• Factors of pollution :

- Organic materials;

- Fine particles brought by wind;

- Particles ( clay, silt, …) going up from the formation;

- Poor drainage;

- Materials falling from the wagons;

- Wear and fragmentation of the stones due to dynamic

loads and tamping operations.

9 Ballast: Issues and Challenges International Workshops 05-06.12.2013

Ballast renewal : decision process


3. Renewal Process

1) Proposal for ballast to be relaid.

- line importance

- age and type of ballast ( according to technical inventory);

- track geometry degradation ;

- local problems ( mud spots,

poor drainage, …)

- tamping intervals to restore

track geometry ;

- together with sleeper renewal.

Ballast renewal


3. Renewal Process

2) Validation process.

Borings with a special boring

machine.

D:/Transfer/Carotteuse/Unimog/Proffund/S5001751.JPG



Ballast renewal


3. Renewal Process

- Borings every 100 m to a

depth of 1,5 m under top

of the rail

visual examination of

samples (thickness of sound

and clogged ballast, nature of

subsoil, …) ;

- Every 400 m, grain size

distribution analysis in

laboratory (percentage of

elements smaller than 22,4

mm);




Ballast renewal – Decision process


3. Renewal Process

Criteria based on expert

committe ERRI D 182 : 1995

( European Rail Research

Institute , former research

institute of UIC)

« Ballast has to be cleaned

when the percentage of

elements passing through a

sieve of 22,4 mm is higher

than 30 % in weight). ».




Ballast renewal – Boring results


3. Renewal Process

Clogged ballast thickness

Top level of ballast

Level cess

Boring depth

Percentage of elements < 22.4mm if > 30 % then renewal

if < 30 % then no renewal

Hectometer Localisation




Ballast renewal


4. In the future

Renewal of a section

based on degradation

rate of the geometrical

parameters of the track.

The track geometry

recording car runs 2

tilmes/year on all the

main lines.

It measures the quality

of track levelling every

25 cm and calculates the

standard deviation

(sigma) every 200m.




Ballast renewal – works execution


3. Renewal Process

Planning of the works : contractor, track interception,

logistical part, ballast screening machine, ballast reprofiling,

tamping, stabilization…




Ballast renewal – works execution


3. Renewal Process

Last years production : due to low budget, priority has been given

to renewal works with high influence on safety ( rail, switches and

crossings). It is necessary to increase the quantities for the next

years.

Site’s length

(km) Speed (m/h)

Renewed

length

(km)

Unrenewed

length(km)

Evacuated

product

(x1000 t)

Evacuated

product

per meter

(t/m)

2008 64 118 53 11 56 0.88

2009 74 132 68 6 55 0.75

2010 45 172 44 1 28 0.62

2011 21 137 19 2 18 0.86

2012 18 169 17 1 13 0.72




Ballast renewal – In the future


4. In the future

Use of Ground penetrating radar (GPR) + endoscopic analysis

for proposals validation.





Use of Georadar :

the interpretation of GPR results needs experience !!!



4. In the future

Endoscopic analysis Georadar interpretation

Panda analysis






4. In the future

Georadar vs boring

Advantages Disadvantages

Georadar

- few traffic perturbation

- Continuous measures

- good efficiency

- more and more used

- interpretation difficulties

(relationship between soil

property and radarwave)

- subjective cleanliness

criteria

(visual observation required)

Boring

-Easy interpretation (direct

relationship between

property and granulometry)

- objective cleanliness

criteria

(optional visual observation)

- Substantial traffic

perturbation (necessary traffic

interruption)

- Discontinuous measures

(need extrapolation)

- bad efficiency

- archaic system




02.10.2012 Strategisch plan Bascooup 22

Ballast renewal - Conclusion

The decision process for ballast renewal remains a

difficult thing, it is not a direct safety related process and

often gets less priority;

Several criteria can be used :

Age of ballast;

Rate of track geometry degradation;

Visual examination;

Geotechnical analysis : borings, georadar,…

A linear asset management tool is needed ( track

geometry, borings, georadar, …).

But what are the good criterias ? I hope this seminar can

help us to determine the best technical and economical

methods .

I wish you good and fruitful discussions.

05-06.12.2013 23 Ballast: Issues and Challenges International Workshops

Thank you for

your attention

QUESTIONS ?

Documents

Decision process for ballast cleaning and/or renewal at …railway-science-workshops.org/IMG/pdf/godart_-_decision_process... · Decision process for ballast cleaning and/or renewal