enhanced shear resistance of railtracks...

ENHANCED SHEAR RESISTANCE OF RAILTRACKS WITH

BALLAST-RUBBER COMPOSITES: A LABORATORY STUDY

SITI FARHANAH BINTI S.M JOHAN

A dissertation project submitted in partial fulfilment of the requirement for the

award of the degree in Master of Science in Railway Engineering

CENTRE FOR GRADUATE STUDIES

UNIVERSITI TUN HUSSEIN ONN MALAYSIA

2015

v

ABSTRACT

Railway ballast, which form an integral part of rail tracks, are highly susceptible to

subsistence due to both vibration transmitted by the passing trains, as well as the

influence of the weathering and contamination effect. The resulting subsistence

necessitates regular monitoring and maintenance, involving cost and time consuming

remedial actions, such as stone-blowing and ballast renewal. It would be desirable if

some measure can be taken in minimize the maintenance costs of railway tracks,

consequently to optimizing the passenger comfort. This paper describes the

exploratory work on ballast-rubber composites to enhanced the shear resistance of

rail tracks and identify the effects of ballast exposure to the weathering and oil

contamination. The rubber elements were sourced from tyre inner tubes commonly

used for motorcycles, cut and shaped accordingly to produce strips, shreds and

circular patch respectively and were arranged in various pre-determined

configurations within the ballast layer. Granitic stones of suitable sizes were sieved

and used as representative samples of typical ballasts as the tests were mainly carried

out with a standard direct shear test setup, i.e. shear box measuring 60 mm x 60 mm.

In order to identify the shear resistance deterioration of aggregate-rubber mixture

under poor drainage conditions by soaked a batch of aggregates in water, acid and

lubricant oil to create the effect from moisture and contamination for 14 days prior to

mixing and testing. The direct shear test results indicated that rubber inclusion could

effectively improve the shear resistance of ballasts to various degrees, though the

configurations clearly played an important role in the improvement observed. Both

type of rubber (i.e. new and used), show similar result due to the degradation of used

rubber tube does not too extensive. The shear resistance did not rise dramatically

with the rubber reinforcement. This susceptible shear strain plots indicate ductile

behaviour on the aggregates-rubber composites. This is evident by the linear rise of

shear stress with strain up to approximately 10 % for the control samples (CS) until

it reaches a constant value. Note that all the specimens including CS are in a loose

state during the testing because there were no tamping been applied on the samples.

Overall the circular patch (CP) specimen was the most favourable in all conditions

vi

(dry, acid and oil). At ε = 5%, CP (D) already governed the τave with 170 kPa than

the others. In addition, the friction angle for all configurations (dry, acid, oil) was in

the ranged 87◦- 88

◦ with the critical specific volume, vcrit was 2.160. It was followed

by the ST (H), which was found to allow better deformation capability with

increased ductility of the composite, while the shreds (SH) absorbed impact and

reduced breakages of the ballasts. Both mechanisms contributed to the reduced

overall subsistence, accompanied by an increase in the shear resistance. The

inclusion of rubber elements apparently prevented the dilation of the granular

material when approaching the shear failure and the reducing the settlement.

vii

ABSTRAK

Balast keretapi, merupakan sebahagian daripada infrastruktur landasan kereta api. Ia

sangat terdedah pada kerosakan disebabkan daripada getaran dari keretapi berlalu,

serta balast akan pecah apabila beban dikenakan berulangan serta pengaruh dari

cuaca dan kesan pencemaran terutamaya dari minyak yang tertumpah dari gearabak

kerata api.. Maka, pemantauan secara berkala amat diperlukan dan kekerapan

penyelenggaraan bertambah yang akan melibatkan kos yang tinggi serta makan masa

untuk pemulihan. Antara contoh penyelenggaraan dan pemulihan landasan keretapi

seperti „stone-blowing’dan pembaharuan balast. Ianya sangatlah wajar jika terdapat

langkah-langkah yang boleh diambil untuk mengurangkan haus dan lusuh daripada

kesan lalu lintas kereta api untuk memanjangkan jangka hayat balast. Kajian ini

bertujuan untuk mengetahui penggunaan elemen getah dalam tangani masalah ini

serta keaadan batu yang berbeza. Elemen getah digunakkan adalah daripada tiub

motosikal yang dipotong dan dibentukkan dengan sewajarnya untuk menghasilkan

pelbagai konfigurasi untuk kajian ini. Batuan granite dengan saiz yang sesuai telah

disaring dan digunakan sebagai sampel yang mewakilikan balast biasa telah banyak

dijalankan dengan kaedah kotak ricih yang berukuran 60 mm x 60 mm. Bagi

mengenal pasti kebolehkerjaan dengan campuran batu-getah akan direndam asid dan

minyak pelincir untuk mewujudkan kesan dari kelembapan dan pencemaran selama

14 hari sebelum pencampuran dan ujian. Tiub getah dipotong dan dicincang dengan

sewajarnya untuk menghasilkan jalur dan corak-carik masing-masing, dan telah

disusun dalam pelbagai konfigurasi yang telah ditentukan dalam lapisan balast.

Keputusan ujian ricih langsung menunjukkan bahawa penggunaan getah amat

berkesan dengan meningkatkan rintangan ricih balast untuk pelbagai darjah, dengan

susunan sampel. Ia juga memainkan peranan penting dalam peningkatan yang

diperhatikan. Ini dapat dilihat dengan peningkatan tegasan ricih dengan tekanan

sehingga kira-kira 10% bagi CS sehingga ia dalam nilai yang tetap. Tambahan

bahawa semua sampel termasuk CS berada dalam keadaan longgar semasa ujian.

Keseluruhan kajian ini menunjukkan bahawa CP adalah contoh yang paling baik

dalam semua keadaan (kering, asid dan minyak). Pada ε = 5%, CP (D) telah ditadbir

viii

τave dengan 170 kPa daripada yang lain. Di samping itu, sudut geseran untuk semua

konfigurasi (kering, asid, minyak) adalah 87◦- 88

◦ dengan specific volume, vcrit adalah

2.160. Ia diikuti oleh ST (H), didapati berkeupayaan untuk ubah bentuk yang lebih

baik dengan kemuluran meningkat daripada komposit, manakala corak-carik (SH)

memberi kesan penyerapan impak terhadap pepecahan terhadap balast dapat

dikurangkan. Keseluruhan dalam kajian ini mendapati bahawa membenarkan

keupayaan ubah bentuk dengan kemuluran yang meningkat, Kedua-dua mekanisme

ini telah menyumbangkan kepada penggurangan sara hidup secara keseluruhan, ia

juga telah meningkatan rintangan ricih.

ix

CONTENTS

ACKNOWLEDGEMENTS iv

ABSTRACT v-vi

ABSTRAK vii-viii

LIST OF TABLES xii

LIST OF FIGURES xiii-xv

LIST OF EQUATIONS xvi

LIST OF SYMBOLS xvii

LIST OF APPENDICES xviii-xix

CHAPTER 1 INTRODUCTION

1.1 General 1-6

1.2 Problem Statement 6-7

1.3 Scope of Study 8

1.4 Aim and Objectives 9

1.5 Significance of Study 9

1.6 Organisation of the Dissertation 10

1.7 Summary 10

CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 11

2.2 Rail track

2.2.1 Track Components 11-13

2.2.2 Track Forces 13-14

2.2.3 Track Maintenance 14-15

2.3 Ballast

2.3.1 Ballast Properties 16

2.3.2 Functions of Ballast 17

2.3.3 Ballast Specification and Testing 17-18

2.3.4 Ballast Degradation and Fouling 18-19

2.4 Particle Breakage on Aggregates 19-21

2.5 Ballast Contamination 22-23

2.5.1 Acid rain effect 23-24

x

2.5.2 Lubricant oil effect 24-25

2.6 Rubber Tyres 25-26

2.6.1 Rubber tubes 27-28

2.6.2 Shredded Tyres 29

2.6.3 Strip rubber 30

2.6.4 Crumb rubber 30-31

2.7 Shear stress-strain relationship

2.7.1 Shear stress 31

2.7.2 Shear strain 31-32

2.7.3 Stress-strain relationship for aggregates 32-33

2.8 Shear strength of granular materials 33-34

2.9 Shear strength for granular-rubber mixtures 34-35

2.10 Summary 35-36

CHAPTER 3 RESEARCH METHODOLOGY

3.1 Introduction 37-38

3.2 Raw materials

3.2.1 Ballast aggregates 39

3.2.2 Rubber tube 40

3.2.3 Hydrochloric acid (HCL) 41-42

3.2.4 Lubricant oil 42-43

3.3 Physical properties tests

3.3.1 Particle size distribution 43-45

3.3.2 Specific gravity 45

3.3.3 Particle shape 46-47

3.3.4 Aggregates impact value 47-48

3.4 Methodology

3.4.1 Preparation of aggregates 48-49

3.4.2 Preparation of rubber elements 50-52

3.4.3 Direct shear test 53-57

3.5 Summary 57-58

xi

CHAPTER 4 RESULTS AND DISCUSSIONS

4.1 Introduction 59

4.2 Physical properties of material 60

4.2.1 Particle size distribution 60-62

4.2.2 Specific gravity 62

4.2.3 Aggregates shape (flakiness & elongation index) 63

4.2.4 Aggregates impact value (AIV) 63-64

4.3 Particle breakage 64-65

4.4 Direct shear test

4.4.1 Comparison between new and used rubber tube 65-71

4.4.2 Comparisons between all configurations for dry 71-81

specimens

4.4.3 Comparisons between all configurations for acid 82-90

specimens

4.4.4 Comparisons between all configurations for oil 91-99

specimens

4.4.5 The effect of moisture and contamination 100-101

4.5 Summary 102

CHAPTER 5 CONCLUSIONS AND RECOMMENDATION

5.1 Conclusion 103-104

5.2 Recommendations 104

REFERENCES

APPENDICES

VITA

PUBLICATIONS

xii

LIST OF TABLES

2.1 The specification for ballast particle size distributions 18

3.1 Properties of HCL 39

3.2 Details of configurations 49

4.1 Observation data from dry sieving 57

4.2 Result of specific gravity 58

4.3 Summary of flakiness and elongation index 59

4.4 Summary of Aggregates Impact Value (AIV) 60

4.5 Summary of data for CS (D), NRT (D) and URT (D) specimens 70

4.6 Summary of ɛ =5% corresponding τave for dry specimens 73

4.7 Summary of data for dry specimens in all configurations 81

4.8 Summary of ɛ =5% corresponding τave for acid specimens 83

4.9 Summary of data for acid specimens in all configurations 90

4.10 Summary of ɛ =5% corresponding τave for oil specimens 92

4.11 Summary of data for oil specimens in all configurations 99

4.12 Summary of failure envelope for all configurations 101

4.13 Summary of friction angle for all configurations 101

xiii

LIST OF FIGURES

1.1 ETS KTM at KL Sentral Station 2

1.2 KLIA Express at Salak Tinggi Station 2

1.3 KL Monorail at Bukit Nanas Station 3

1.4 LRT Rapid KL at Kelana Jaya Station 3

1.5 Typical infrastructure for ballasted track 4

1.6 Rail track Infrastructure 4

1.7 Rail track infrastructure 5

1.8 Tracks fouls due to ballast degradation and contamination 6

2.1 Typical of railway track components 12

2.2 Principle of track structure for longitudinal structure 12

2.3 (a) Layout of track forces 14

2.3(b) Layout of track forces 14

2.4 Stone blowing wagon 15

2.5 Fouling ballast 19

2.6 Ballast breakage index (BBI) calculation method 21

2.7 Shape of ballast particle changes after the force contact 21

2.8 Ballast contamination due to clay pumping in Ashfield,

New South Wales, Australia 23

2.9 Ballast contamination due to coal contamination in

Rockhampton, Queensland, Australia 23

2.10 Ballast gravels contaminated by lubricant oil 25

2.11(a) Structure of tyres 25

2.11(b) Component of tyre 25

2.12 Structural comparison of tube and tubeless 28

2.13 Rubber inner tube 28

2.14 Rubber shreds 29

2.15 Strip rubbers 30

2.16 Crumb rubber 31

2.17 Shear stress –strain relationship 32

xiv

2.18 Shear plane for granular particles in shear box 34

3.1 Methodology flow chart 36

3.2 Aggregates for direct shear test (6.3 mm) 37

3.3 Rubber tube 38

3.4(a) Hydrochloric acid (HCL) 40

3.4(b) Apparatus and chemical for diluting concentrated HCL 40

3.5 Acid preparation 40

3.6 Mechanical sieve machine 43

3.7 Aggregate impact test apparatus 46

3.8 Specimens of aggregates (gravels) 47

3.9 Configurations of rubber tube 48

3.10 Illustration for ST with gravels in shear box 49

3.11 Illustration for SH with gravels in shear box 50

3.12 Illustration for CP with gravels in shear box 50

3.13 Mohr-Coulomb failure envelope 52

3.14 Direct shear machine and instruments 52

3.15 Rubber inclusions in various configurations 53

4.1 Particle size distribution of ballast aggregates used in DST 62

4.2(a) Stress-strain curves 67

4.2(b) Vertical-horizontal displacement of dry specimens for

NRT (D) and URT (D) 67

4.3 (a) Volumetric strain, ɛvol - shear strain, ɛ of dry specimens for

NRT (D) 68

4.3 (b) Volumetric strain, ɛvol - shear strain, ɛ of dry specimens for

URT (D) 68

4.4 (a) Specific volumes, v-shear strain, ɛ of dry specimens for

NRT (D) 69

4.4 (b) Specific volume, v-shear strain, ɛ of dry specimens for

URT (D) 69

4.5 Failure envelopes for CS (D), NRT (D) and URT (D) specimens 70

4.6 Sketches of specimens based on results from Table 4.6 72

4.7 Sketch of the aggregates movement (dilation) 74

xv

4.8 Sketches of the aggregates rolls over during shearing 74

4.9 (a) Stress – strain, (b) Vertical-horizontal displacement for CS (D) 74

4.10 (a) Stress – strain, (b) Vertical-horizontal displacement for ST(V)_D 75

4.11 (a) Stress – strain, (b) Vertical-horizontal displacement for ST(H)_D 75

4.12 (a) Stress – strain, (b) Vertical-horizontal displacement for SH(C)_D 76

4.13 (a) Stress – strain, (b) Vertical-horizontal displacement for SH(F)_D 76

4.14 (a) Stress – strain, (b) Vertical-horizontal displacement for CP_D 77

4.15 Volumetric strain-shear strain for dry specimens in all configurations 78

4.16 Specific volume, v for dry specimens in all configurations 79

4.17 Failure envelope for dry specimens in all configurations 80


4.19 (a) Stress – strain plot, (b) Vertical-horizontal displacement for CS (A) 84

4.20 (a) Stress – strain plot, (b) Vertical-horizontal displacement for ST (V) 85

4.21 (a) Stress – strain plot, (b) Vertical-horizontal displacement for ST (H)_A 85

4.22 (a) Stress – strain plot, (b) Vertical-horizontal displacement for SH (C)_A 86

4.23 (a) Stress – strain plot, (b) Vertical-horizontal displacement for SH (F)_A 86

4.24 (a) Stress – strain plot, (b) Vertical-horizontal displacement for CP_A 87

4.25 Volumetric strain-shear strain for acid specimens in all configurations 88

4.26 Specific volume (v)-shear strain for acid specimens in all configurations 89

4.27 Failure envelope for acid specimens in all configurations 90


4.29 (a) Stress-strain plot, (b) Vertical-horizontal displacement for CS_O 93

4.30 (a) Stress – strain plot, (b) Vertical-horizontal displacement for ST(V)_O 94

4.31 (a) Stress – strain plot, (b) Vertical-horizontal displacement for ST(H)_O 94

4.32 (a) Stress – strain plot, (b) Vertical-horizontal displacement for SH(C)_O 95

4.33 (a) Stress – strain plot, (b) Vertical-horizontal displacement for SH(F)_O 95

4.34 (a) Stress – strain plot, (b) Vertical-horizontal displacements for CP_O 96

4.35 Volumetric strain-shear strain for oil specimens in all configurations 97

4.36 Specific volume (v)-shear strain for oil specimens in all configurations 98

4.37 Failure envelope for oil specimens in all configurations 99

xvi

LIST OF EQUATIONS

2.1 Ballast Breakage Index (BBI) 20

2.2 Shear Strength 33

3.1 Molarity of Chemicals 39

3.2 Uniformly Coefficient 42

3.3 Coefficient of Curvature 42

3.4 Mass Passing 42

3.5 Cumulative Percentage Passing 42

3.6 Specific Gravity 43

3.7 Flakiness Index 44

3.8 Elongation Index 45

3.9 Aggregates Impact Value 45

3.10 Shear Failure 51

3.11 Shear Stress 52

4.1 Young’s Modulus 62

4.2 Poisson’s Ratio 63

4.3 Volumetric strain, ɛvol 64

4.4 Shear strain, ɣ 64

4.5 Specific volume, v 64

xvii

LIST OF SYMBOLS

LRT Light Rail Transit

ERL Express Rail Link

KTM Keretapi Tanah Melayu

KL Kuala Lumpur

ROW Right of Way

KLIA Kuala Lumpur International Airport

BS British Standard

AREMA American Railway Engineering and Maintenance

ASTM American Standard Testing Method

PSD Particle Size Distribution

BBI Ballast Breakage Index

pH Water Properties

HCL Hydrochloric Acid

Cu Uniformly Coefficient

Cc Coefficient of Curvature

Gs Specific Gravity

τ Shear Stress

ɣ Shear Strain

ɛ Strain

ϕ Friction Angle

σ Total Stress

∆h Horizontal Displacement

∆v Vertical Displacement

CS Control Samples

ST Strips

SH Shreds

CP Circular Patch

kPa KiloPascal

R2

Regression

CL Cross Line

xviii

LIST OF APPENDICES

A 1-1 Graph for shear stress-strain for dry specimens

(All configurations) (used tube rubber)

A1-2 Graph for shear stress-strain for acid specimens


A 1-3 Graph for shear stress-strain for oil specimens


B 1-1 Graph of failure envelope for dry specimens


B 1-2 Graph of failure envelope for acid specimens


B 1-3 Graph of failure envelope for oil specimens


C 1-1 Graph of volumetric strain-shear strain for dry specimens


C 1-2 Graph of specific volume-shear strain for dry specimens


C 1-3 Data of volumetric strain and specific strain for dry specimens


D 1-1 Graph of volumetric strain-shear strain for acid specimens


D 1-2 Graph of specific volume-shear strain for acid specimens


D 1-3 Data of volumetric strain and specific strain for acid specimens


E1-1 Graph of volumetric strain-shear strain for oil specimens


E 1-2 Graph of specific volume-shear strain for oil specimens


E 1-3 Data of volumetric strain and specific strain for oil specimens


xix

F 1-1 Data from direct shear test for dry specimens


F 1-2 Data from direct shear test for acid specimens


F1-3 Data from direct shear test for oil specimens


CHAPTER 1

INTRODUCTION

1.1 General

Railway line in Malaysia has been upgraded either in their system or infrastructure in

order to parallel with the country development. Based on Lowtan (2004), there are

several railway transport services in Malaysia such as heavy rail, express rail link

(ERL), light rail transit (LRT) and monorail shown in Figure 1.1, 1.2, 1.3 and 1.4.

Lowtan (2004) mentioned that Keretapi Tanah Melayu (KTM) is the only

heavy rail operator in Malaysia providing services for passengers and freight. ERL

is the high speed train in Malaysia which link between KL Sentral and the Kuala

Lumpur International Airport (KLIA). Only the KTM and ERL provide ballasted

track along the route as their right of way (ROW). Meanwhile, LRT and monorail

could be found in the urban area and both services have their own concrete structure

as their route (Lowtan, 2004).

2

Figure 1.1: ETS KTM at KL Sentral Station (www.ktmb.com.my, 2015)

Figure 1.2: KLIA Express at Salak Tinggi Station (malaysiagazette.com, 2015)

http://www.ktmb.com.my/

3

Figure 1.3: KL Monorail at Bukit Nanas Station (Molon A., 2015)

Figure 1.4: LRT Rapid KL at Kelana Jaya Station (Schwandal R., 2007)

The rail track infrastructure shown in Figures 1.5, 1.6 and 1.7 are termed

ballasted track. The superstructure consists of rail, fastening, sleeper and it acts as

the main function in the rail track foundation (Bonnett, 2005). The substructure such

as ballast, subballast and subgrrade provides a foundation layer to support the

superstructure. Indraratna et al. (2007) also pointed out that the superstructure attains

optimum performance by transmitting the traffic load to the subgrade via the

substructure.

4

Figure 1.5: Typical infrastructure for ballasted track (Dahlberg, 2004)

Figure 1.6: Rail track Infrastructure (Depot KTM Gemas, 2013)

5

Figure 1.7: Rail track infrastructure (Station in KTM Gemas, 2013)

The term „ballast‟ used in railway engineering refers to the coarse aggregates

above the subballast layer and subgrade. Studies carried out by Bhanitiz (2007) and

Indraratna et al. (2001) reported on the behaviour of ballast deformation and

breakage under static and dynamic loading. Khabbaz and Indraratna (2009) also

found ballast to break down under the cyclic load from heavy trains as shown in

Figure 1.8.

As summarised by Selig and Waters (1994), vertical and horizontal

movements caused by traffic loads are attributed mainly to the deformation and

densification of the ballast. Rail track performance depends on the ballast as the

main material and leads to poor ride quality, requiring either speed restrictions or

maintenance to realign the tracks (Anderson and Key, 2000).

Ballast has to be tough, dense, weather-resistant and mechanically stable

(Dahlberg, 2004). Generally, rail track ballast is exposed to the dry and wet weather,

as well as the contamination caused by the braking wheels and oil leak from the

train. There could lead to negative effects on the rail track performance. Thus, it is

very important to ensure the quality and durability of ballast from such deterioration.

6

Figure 1.8: Tracks fouls due to ballast degradation and contamination

(ARTC, 2015)

1.2 Problem statement

In railway engineering, ballast play a crucial part in transmitting and distributing the

wheel load to the rail track foundation as well as support the rails and sleepers

(Indraratna et al., 2007). Ballast are highly susceptible to subsistence due to both

vibration transmitted by the passing trains, as well as the breakage of the ballasts

themselves with repeated impact. Based on conventional triaxial tests, Janardhanam

and Desai (1983) concluded that the particle size of ballast significantly affect the

overall resilient modulus, volumetric and shear behaviour. It follows that track

settlement is very much dependent on the ballast quality and its response to traffic

load.

Tennakoon et al. (2014) stated that contamination on ballast layer influence

the conditions of its drainage and shear strength. This contamination could decrease

an overall shear strength and impede the drainage of the track. According to

Khabbaz and Indraratna (2009), the main factors on ballast breakage that related to

the particles and loading conditions as example the confining pressure, ballast

7

gradation, presence of water or ballast moisture, dynamic loading pattern and the

frequency.

Ballast is able to allow the track misalignment caused by from the lateral

movement from the passing trains on curved track (Lam and Wang, 2001). In

addition, weather and water also could cause damage and crushing of ballast by axle

weight. The damage on ballast will lead to tracks “pumping” with the train‟s

passing, which eventually causes damage to the rail or sleepers (Railway Technical,

2014). Track “pumping” is a continuous loop of ballast and subgrade movement

which creates on up -down motion. This affects the comfort of passengers on board

as well as imposing additional wear on the rolling stock (Esveld, 2001). Fouling is

the proven ballast when it starts to damage, contamination, gradation changes and

performance reduction to suffer form. This condition affects the ballast size

distribution under the sleepers in certain areas along the rail track, resulting in

uneven support of the rail tracks (Siddique and Naik, 2004).

Degradation of ballast also contributes to increase frequency of maintenance

and rehabilitation cost too. It would be desirable if measures could be taken to

minimize the wear and tear effect of the rail traffic, consequently prolonging the life

span of the ballast. This because the wear and tear on the ballast could increase the

maintenance cost by realign the rail, replacement of tracks. Khabbaz and Indraratna

(2009) highlighted that the main causes of ballast degradation include excessive

dynamic loading, vibration, temperature, moisture fluctuation and impact load from

severe braking.

Rubber Manufacture Association (2006) had reported that discarded rubber,

especially waste tyres significantly increased the volume of solid waste. Some of

these rubber tyres and tube are left stockpiled in landfills or illegally dumped and

this could be harmful to the environment. It results in environmental hazards

worldwide and has indeed become a serious problem in many countries. The

quantity of used tyre can be beneficially used in geotechnical applications because

8

the tyres do not decompose and it is susceptible to fire hazards (Vinot and Singh,

2013).

1.2 Scope of study

This study is an exploratory work on the ballast-rubber tube composites

which involves measurements with the direct shear test. The rubber inclusions are

incorporated in the specimen in various configurations. The use of new inner tube as

the rubber elements was to ensure the consistency of the specimen tested.

Rail track ballast regularly exposed to the weather and oil contamination. Oil

contamination could happen due to the fuel leak and friction from wheel braking.

Simulations of the ballast with these conditions were achieved by submerging the

ballast with water, acid and lubricant oil for two weeks (14 days). A total of 132

specimens were tested:

i) Control sample (dry, wet, acid and lubricant oil)

ii) Dry aggregates + rubber tube (new and used)

iii) Wet aggregates + rubber tube (new and used)

iv) Hydrochloric acid aggregates + rubber tube (new and used)

v) Lubricant oil aggregates + rubber tube (new and used)

The shear box test was conducted on specimen of various configurations

such as coarse and fine shreds, vertical and horizontal strips and circular patch,

where three vertical stresses were applied respectively for each specimen.

9

1.4 Aim and objectives

The ultimate goal of this study is to verify that rubber inclusion could be more

effectively improve the shear resistance in ballast layer with various configurations.

The objectives for this research work are:

a) To determine the shear resistance of ballast aggregates with rubber inclusions

in various configurations through direct shear test.

b) To identify the effect of simulated exposure to moisture, acid and oil

contamination on the composite material (ballast-rubber mix).

1.5 Significance of study

The importance of this study is to determine the potential of rubber inclusions in

increasing the shear resistance of ballast aggregates in several predetermined

configurations. By having the rubber inclusion in the ballast layer, shear resistance

could be increased, consequently reducing the wear and tear for better and longer

performance.

Considering the cost-effectiveness, availability and practicality of ballast,

advancement in railway technology would arguably outrun the material substitution

or total replacement in the near future (Eisenmann, 1995). The rubber inclusion

could also enhance the shear resistance under exposure to the effects of chemical

attack and natural weathering. However, analysis of the composite‟s performance

under dynamic load was carried out too by adopting a number of empirical

correlations from part related work. In this study, only static test was conducted on

the ballast-rubber composites.

10

1.6 Thesis outline

Outline of this dissertation is summarized as follows. Chapter 1 presents the

problem statement, objectives and scope of the study. Chapter 2 presents the

literature review on the project, which included the background and significance of

the ballast aggregates as the part of railway track components and the properties of

materials. It also includes reviews on the rubber inclusion with granitic aggregates

and granular materials by using the standard direct shear box.

Chapter 3 presents details of the measurements and tests for collecting the

laboratory test results. Chapter 4 analyses and the results mainly from shear box

test. The discussions include assessment from the results obtained. Chapter 5

presents the conclusions and recommendation for future work.

1.7 Summary

This chapter highlights the general background of this study, including the aims and

objectives of the research, followed by an outline of the thesis.

CHAPTER 2

LITERATURE REVIEW

2.1 Introduction

This chapter presents a literature review related to ballast and rubber elements. This

literature review focuses on the following sections:-

a. Ballast and the rail track environment

b. Particle breakage and the associated with the ballast degradation

c. Ballast contamination

d. Rubber elements and its related functions

e. Shear strength associated with granular materials and rubber mixtures

2.2 Rail track

2.2.1 Track components

Railway track were laid down since in eighteenth century which was wagon that

used for carried collieries and quarries (Bonnett, 2005). Since then lot of invention

had been made in the railway engineering till now especially for railway tracks and

their infrastructures. Components in railway track are dividing by two main

components such as superstructure and substructure. Superstructure normally

consists of rails, sleepers, rail pads and fastening. Meanwhile for substructure

components consists of ballasts, sub-ballast and subgrade layered as shown in Figure

2.1 and 2.2 for typical components in railway track.

12

Figure 2.1: Typical of railway track components (Esveld, 2001)

Figure 2.2: Principle of track structure for longitudinal structure (Esveld, 2001)

The rails made from the steel girders that carried the axle load of train

(Bindra, 1976). Therefore, the material for rails should be required in qualities of

strength, fatigue endurance, wear and the resistance in corrosion (Bonnett, 2005).

The functions of rails were to distribute the wheel load from train and transfer it to

the sleepers system then to the substructure system. Fastening system for rails was

between rails and sleepers in order to resists the forces from vertical, lateral,

longitudinal and overturning movements of the rails (Wee, 2004).

Meanwhile, the sleepers which in monobloc shape is to spread the wheel

loads to ballast then transmits the lateral and longitudinal forces also functions to

hold the rails gauge and inclination (Bonnett, 2005). Subgrade is the last support to

sustain and distribute the resultant downward dynamic loading along its infinite

13

depth (Wan Azlan, 2012). According to Bhanitiz (2007), subgrade was the track

foundation which from the existing natural soil and also similar with other

foundation behaviour that has excessive settlement should be avoided. Li and Selig

(1995) mentioned that the excessive track settlement is generally due to the

accumulated plastic deformation of ballasts and substructures layers. However, this

gradual accumulation of permanent strains with traffic loads is often overlooked as

dynamic records often show negligible elastic deformation of the track support

system, where only static measurements reveal the accrued plastic strains (Yoo and

Selig, 1979). Furthermore, Dwyer-Joyce et al. (2003) simulated rail-wheel contact

with ballast and found that crushed ballast do not only indent and roughen the metal,

but inadvertently increase the traction level and reduce the residual fatigue life of the

contact.

2.2.2 Track forces

According to Bhanitiz (2007), the railway track has some forces such as vertical,

lateral and longitudinal directions act on the track structure due to the movement

traffic and the changing temperature. The acceleration and braking from the trains

had created the longitudinal forces and gave the thermal expansion or contraction of

the rails.

While for lateral forces, Bhanitiz (2007) had stated that lateral forces usually

comes from the lateral wheel force because of the friction between rail and wheel.

As shown in Figure 2.3 (a) and (b), vertical forces can be subdivided into downward

and upward force. Wan Azlan (2012) stated that railway track structures is primarily

analysed and over designed by considering the static and dynamic loads on the track

structures is to avoid from the excessive loading which could induce damage to the

railway foundation..

14

Figure 2.3 (a): Layout of track forces (Bhanitiz, 2007)

Figure 2.3(b): Layout of track forces (Bhanitiz, 2007)

2.2.3 Track maintenance

The railway track should have some maintenance in order to provide good

performance and comfort to the train passengers. The track ballast in railway system

exists for more than 150 years in the railway industry and it has become the basic

thing in track design (Edwards, 1990).Therefore, the maintenance usually takes plan

in one to three years.

According to Dahlberg (2004), because of the settlement of railway tracks,

regular maintenance work is necessary, for rail tracks without proper maintenance

could dangerous, such as resulting in train derailment.

15

Maintenance techniques had reached the high standard of development with

adoption of mechanization in most of the operations (Edwards, 1990).The

maintenance for the railway track have two methods such as tamping and

stoneblowing, as shown in Figure 2.4. The frequency of maintenance the track based

on the frequency of train runs in a year. It depends on the defects on the rail track

and the foundation. Due to the new technology, the defects or deformation on the

track can be detect by using the track circuit which transfer the information to the

control room operators to make the action.

According to Khabbaz and Indraratna (2009), there are two types of track

such as slab track and ballasted track. For slab track, it can be more effective in the

cost when the life-cycle maintenance were considered. Slab track also could provide

some advantages such as free of maintenance, less traffic disruption and no dust

emission. However, this type of track may not be favourable due to the high cost in

construction. As such, ballast track is still widely used due to its effectiveness,

efficiency and relatively easy maintenance.

Figure 2.4: Stoneblowingwagon (www.harsco.com)

http://www.harsco.com/

16

2.3 Ballast

2.3.1 Ballast properties

In railway track components, ballast is the most important for the track that placed

on top of the track subgrade in order to support the weight of track structure and the

dynamic loading from passing trains. Usually ballast providing tensionless elastic

support, a free-draining coarse aggregate layer typically composed of crushed stones,

gravel and crushed gravel (Wan Azlan, 2012).

According to Pires and Dumont (2013), the depth of ballast structure in rail

track is 300-500 mm. Ballast should in angular shape of gravel that has granular

fractions between 22 mm and 63 mm. Materials for the ballast mostly include

dolomite, rheolite, gneiss, basalt, granite and quartzite which is composed of

medium to coarse gravel sized aggregates (Indraratna et al., 2007). Ballast is made

up of stones from granites or a similar that should be rough in shape to improve the

locking of stones. In Malaysia, granite is commonly used as track ballast, as can be

seen at KTM and ERL operations.

Good quality materials for railway ballast are angular shape, high specific

gravity, high shear strength, high toughness and hardness. The high resistance to the

weathering, rough surface and minimum hairline cracks also important properties of

railway ballast (Khabbaz and Indraratna, 2009). The important elements in the

railway track that related to the mechanical and hydraulic properties also the

efficiency in the maintenance.

17

2.3.2 Functions of ballast

Based on Selig and Waters (1994), Mundrey (2000), Esveld (2001), Dahlberg

(2003), Kaewunruen and Remennikov (2008), the fundamental functions for ballast

in railway track engineering can be summarised as follows:-

(a) Provides and resists vertical, lateral and longitudinal forces stability to track.

(b) Distributes the load from sleepers in order to resist the subgrade from high

stresses so that there will not have permanent settlement occur on track.

(c) Ballast also could absorb the shock from dynamic loading by providing

resilience bed for sleeper.

(d) Facilitate water drainage flow from track structure.

(e) It also gives easy maintenance surfacing and lining operations.

(f) Protects formation against rains and winds.

(g) Protect the sleepers form capillary moisture of structure.

(h) It can slow the vegetation growth and the fouling effect can be resist from

surface-deposited materials.

(i) Reduce bearing stresses from the sleepers to acceptable stress levels for

underlying layers

(j) Allow optimum global and local settlement

2.3.3 Ballast Specification and Testing

All the specification and types of testing that need to conduct should be referring to

the standard. In Malaysia, standards used British Standard (BS), United States

(AREMA) or Japanese Standard. The standard usage is based on client demand and

suitable for this country. In this case, ballast specification and testing by referring to

British Standard and American Standard Testing method (ASTM).

This specification part purposely to ensure the ballast materials is from good

quality when in testing after manufacturing process by the quarry. Based on BS EN

13450 (2013), which are five specifications for ballast properties to define as the

18

ballast track specification which are ballast grading, Los Angeles Abrasion (LAA),

micro-Deval attrition (MDA), flakiness index and elongation. The particle size

distribution for ballast is shown in Table 2.1.

Table 2.1: The specification for ballast particle size distributions

2.3.4 Ballast degradation and fouling

Ballast could be damaged because of the cementation with the accumulation of fines

which occur from the tamping action and other loads. This could reduce the ballast

size in certain area under sleepers and along the railway track. It also could result in

uneven support of the railway (Lam and Wang, 2011).

According to Khabbaz and Indraratna (2009), the degradation on ballast can

occurs because of the excessive dynamic loading and vibration, temperature and

moisture fluctuation and also impact load on ballast due to severe braking. Three

ways in ballast particles to degradation as following:-

(a) Small-scale asperities by grinding off (abrasion).

(b) Fracture or split of individual particles.

(c) The fragments and angular projection by breaking of that influence the initial

settlement.

Square Mesh Sieve (mm) Cumulative % by mass passing BS Sieve

6.3 100

50 70-100

40 30-65

31.5 0-25

22.4 0-3

32-50 ≥50

19

When ballast start damaged, contaminated, gradation changes and

performance reduce then this process called as fouling. The effect for the fouling

ballast depends on the types of the material, the degree it fouling and water contents

(Wee, 2004).

Drainage is one of the main purposes in railway ballasted track by providing

the large voids and storage of fouling materials. This could be happen because when

the fouling degree increases, large voids will fill in with slowly by the fouling

materials and the permeability of ballast become decrease such in Figure 2.5.

Therefore, this will create pore water pressure and the fouling materials mix with the

water (Wee, 2004).

Figure 2.5: Fouling ballast (Indraratna et al. 2014)

2.4 Particle breakage on aggregates

According to Bhanitiz (2007), particle breakage in an aggregate probably increases

when the macroscopic stress been applied, the increasing in particle size and the

reduction in number of contacts with other particles. When there has effect on the

sizes, the particle become larger and the strength will reduced.

Furthermore, the loads have been distributed through in many contact points

on the surface and then reducing the tensile stress. On the other hand, if the number

in coordination effects had dominates over the size effect, then small particles could

20

break easily. Based on conventional triaxial test, Janardhanam and Desai (1983)

concluded that the particle size of ballast significantly affect the overall resilient

modulus, volumetric and shear behaviour. It follows that track settlement is very

much dependent on the ballast quality and its response to traffic load.

There has an alternative that introduced by Indraratna et al. (2005), about the

ballast breakage index (BBI) based on particle size distribution (PSD) curves. BBI is

calculating on the basics changes in fraction passing a range of sieve as shows in

Figure 2.6. The increasing in degree of breakage could cause the PSD curve to shift

further towards the smaller particles size region on the PSD conventional plot. At

area A between the initial and final, PSD increases results in a greater BBI value. If

BBI has a lower limit of 0, means that there has no breakage happen then the limit

must be upper limit of 1. BBI can be calculated with the Equation 2.1 by referring to

the linear particle size axis. Figure 2.7shows when the ballast reaction or condition

after received some contact forces to the ballast surface.

Where,

A = area

B = the potential breakage or area between the arbitrary boundary of

maximum breakage and the final PSD.

A

BBI = (2.1)

A + B

21

Figure 2.6: Ballast breakage index (BBI) calculation method

(Indraratna et al. 2005)

Figure 2.7: Shape of ballast particle changes after the force contact

(Bhanitiz, 2007)

22

2.5 Ballast contamination

Contamination on ballast which cause by subgrade pumping and other lubricant for

example coal is one of major problem for track deterioration in many countries over

the world. Tennakoon et al. (2014) stated that any lubricant may induce load bearing

capacity or shear strength on ballast layer reducing and impede the drainage of track.

Ballast contamination could effect on the ballast layer and also transfer the pollutants

into the soil or underground water.

Ballast gravels were also constantly exposed to the other pollutants such as

acid rain because it lay on top of the rail track. Figure 2.8 and 2.9 shows the picture

of ballast contamination due to clay pumping and coal contamination. Other than

that, the contamination frequently happened due to the leaking from fuel tank, grease

dropping and heavy metals which produced from the train. It could occur from the

contact between wheel and rail or wheel and brake pad when braking (Cho et al.

2008).

Ballast also regularly exposed to weathering including the effect of freeze-

thaw, thermal effects, water, water slurries and acid rain. This could cause the ballast

particles breakdown as they are subjected to the mechanical and environmental

factors. In addition, ballast breakdown and fouling over three quarters can occur

during transportation and handling or over time due to chemical interactions (Selig

and Waters, 1994).

23

Figure 2.8: Ballast contamination due to clay pumping in Ashfield, New South

Wales, Australia (Tennakoon et al., 2014)

Figure 2.9: Ballast contamination due to coal contamination in Rockhampton,

Queensland, Australia (Tennakoon et al., 2014)

2.5.1 Acid rain effect

Ballast was constantly exposed to the other pollutants such as acid rain because it lay

on top of the rail tracks. Acid rain contamination or pollution often happens in

Southeast Asia especially in Malaysia. Nordberg et al. (1985) and Spengler et al.

24

(1990) had mentioned the contamination of toxic gasses into the main cause of acid

rain especially in urban and industrial areas.

Acid rain can be any other form precipitation that will create it become

acidic. Means that, acid rain consists of hydrogen ions but in a low pH. Based on

United States Environmental Protection Agency (2012), acid rain primarily

emissions of sulphur dioxide (SO2) and nitrogen oxides (NOx). It occurs when the

gasses reacts in the atmosphere with water, oxygen and other chemicals to form

various acidic compounds. The strongest compounds in rainwater were hydrochloric

acid (HCI), HNO, H2SOl bisulphite and ammonia (NH, HSO,).

2.5.2 Lubricant oil effect

As mentioned before, ballast could be contaminated by grease and lubricant oil due

to the wheel braking and fuel leaking from the train as in Figure 2.10. This

contamination could affect the ballast to become fouling and damage. Lubrication oil

or lube oil is the most commonly widely used because of the possible applications.

There have two basic categories of lube oil which are mineral and synthetic.

Naturally for mineral oils are refined from petroleum or crude oil. The synthetic oils

were manufactured from hydrocarbon or ester oil.

When the ballast layer was contaminated with either coal or oil, the voids

will significantly decrease the track drainage capacity due to the clogging from the

fine particles. This could cause the heaving on the pore water pressure when under

imposed load from train (Tennakoon et al. 2014).

105

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