the effectiveness of coconut coik blanket in

THE EFFECTIVENESS OF COCONUT COik BLANKET IN CONTROLLING

SLOPE EROSION

AIZAT BIN MOHD TAIB @ TAlE

A thesis submitted in partial fulfillment of the requirements for the award of the

degree of Bachelor of Civil Engineering

Faculty of Civil Engineering & Earth Resources

Universiti Malaysia Pahang

DECEMBER 2010

ABSTRACT

A research to determine the effectiveness of coconut coir blanket in

controlling slope erosion was conducted. There were two major division of testing

made. One was the material analysis on the soil sample taken and the coconut coir

blanket used and another was the simulation of rainfall pouring on sloped surface soil

to analyze the erosion rate. Apparently, the division of material testing involved Soil

Mechanics Engineering and Light Structure Engineering. Soil Mechanics

Engineering assisted this research in soil analyzing in terms of the Soil

Classification, Atterberg Limit, Specific Gravity, Shear Strength, Standard Proctor

and Direct Shear testing. On the other hand, Light Structure Engineering focused on

Tensile Strength of the coconut coir blanket. Generally, the major testing was the

simulation of rainfall on the sloped surface soil. The soil sample which was taken

from construction site in Bukit Gambang,. Pahang was distributed into four cases.

The parameters manipulated were the degree of slope, type of vegetation and the

condition of the slope surface. The selected degree of slope were 0°, 100, 20°, 300,

400 and 500. The vegetations planted were based on the norm slopes grasses used

which were the Signal Grass and Japanese Millet. The conditions of the slope surface

were divided into two. They were bare controlled case and protected slope case using

coconut coir blanket. The main parameter which was the application of coconut coir

blanket as the protection to the slope was proven effective. By comparing the bare

controlled slope and the protected slope, the result showed that protected slope using

the coconut coir blanket decreases the erosion rate by the Total Suspended Solids

(TSS) test conducted. The bare controlled slope collected 0.014345 g/L amount of

TSS while protected slope using coconut coir blanket collected only 0.001368 g/L.

The difference of 0.0 12977 g/L TSS amount proved that coconut coir blanket was

effective in controlling slope erosion assisted by the vegetation of Signal Grass

which has longer leaves and gripping fibre roots in increasing the mode of slope

strength.

A

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ABSTRAK

Satu kajian untuk menentukan keberkesanan karpet sabut kelapa untuk

mengawal hakisan cerun telah dijalankan. Terdapat dua bahagian bagi ujikaji yang

dijalankan iaitu analisa ke atas sampel tanah diambil termasuklah sabut kelapa yang

digunakan dan simulasi proses hujan ke atas cerun tanah untuk menganalisa hakisan

cerun. Bahagian ujikaji untuk bahan yang digunakan merangkumi Kejuruteraan

Mekanik Tanah dan Kejuruteraan Struktur Ringan. Kejuruteraan Mekanik Tanah

membantu ujikaji mi dengan usaha menganalisa Pengelasan Tanah, Had Atterberg,

Graviti Tentu, Kekuatan Ricih, Proktor Piawai and ujikaji Ricih Terus. Sebaliknya,

Kejuruteraan Structur Ringan menumpukan kepada ujikaji Kekuatan Tegangan bagi

bahan karpet sabut kelapa yang digunakan. Secara amnya, ujikaji utama adalah

simulasi hujan ke atas cerun tanah. Sampel tanah yang diambil dari kawasan

pembinaan di Bukit Gambang, Pahang dibahagikan kepada empat kes.

Pembolehubah yang dimanipulasikan adalah darjah kecerunan, jenis tumbuhan dan

keadaan cerun itu. Darjah kecerunan yang dipilih adalah 0°, 100, 20°, 30°, 400 dan

50°. Tumbuhan yang ditanam merujuk kepada rumput yang biasa ditanam di

kawasan cerun iaitu Signal Grass dan Japanese Millet. Keadaan cerun telah

dibahagikan kepada dua iaitu kes tanah kosong yang dikawal dan kes cerun tanah

Yang dilindungi. Pembolehubah utama adalah aplikasi oleh karpet sabut kelapa

sebagai pelindung cerun dibuktikan berkesan. Dengan membandingkan cerun kosong

Yang dikawal dengan cerun yang dilindungi, keputusan ujikaji menunjukkan cerun

Yang dilindungi mengurangkan hakisan tanalmya melalui ujikaji Sisa Pepejal

Terampai yang telah dijalankan. Cerun yang kosong mengumpul 0.014345 g/L sisa

pepejal terampai sementana cerun yang dilindungi menggunakan karpet sabut kelapa

mengumpul hanya 0.001368 gIL. Perbezaannya adalah 0.012977 g/L yang

membuictikan karpet sabut kelapa lebih berkesan dalam mengawal hakisan cerun

yang ditanam dengan rumput Signal Grass dimana daunnya yang lebih panjang dan

akar serabutnya yang kuat bagi meningkatkan mod kekuatan cerun.

TABLE OF CONTENT

CHAPTER ITEM PAGE

TITLE

DECLARATION

DEDICATION iv

ACKNOWLEDGEMENT v

ABSTRACT vi

ABSTRAK vii

TABLE OF CONTENT viii

LIST OF FIGURES xiv

LIST OF TABLES xviii

LIST OF SYMBOLS AND ABBREVIATIONS xix

LIST OF APPENDICES xxi

INTRODUCTION

1.1 Background of Research 1

1.2 Problem Statement 3

1.3 Objectives 5

1.4 Scope of Study 6

1.5 Significant of Study 7

vu'

ix

2 LITERATURE REVIEW

2.1 Introduction 9

2.2 Causes of Erosion 10

2.3 Effects of Erosion 11

2.4 Erosion Control 14

2.5 Erosion Control Blanket 16

2.6 Coir Fibre 20

2.6.1 Coir Fibre Processing 21

2.7 Laboratory Testing 23

2.7.1 Particle Size Distribution 23

2.7.2 Moisture Content 24

2.7.3 Atterberg Limit 25

2.7.4 Direct Shear 26

2.7.5 Triaxial Compression 26

2.8 Case Study 27

3 METHODOLOGY

3.1 Introduction 31

3.2 Preparation of Soil Sample and Coconut Coir 33

Blanket

3.2.1 Soil Sample 34

3.2.1.1 Particle Size Analysis 34

3.2.1.2 Specific Gravity 37

3.2.1.3 Atterberg Limits 38

a. Liquid Limit 39

b. Plastic Limit 40

C. Shrinkage Limit 41

3.2.1.4 Standard Proctor Test 43

3.2.1.5 Unconsolidated Undrained Triaxial 45

Test

x

3.2.2 Coconut Coir Blanket 47

3.2.2.1 Tension Test 47

3.2.2.2 Direct Shear Test 48

3.3 Preparation of Slope and Rainfall Simulation Model 48

3.4 Testing 48

3.5 Result Analysis and Discussion 50

4 RESULTS AND DISCUSSION

4.1 Introduction 51

4.2 Soil Analysis 52

4.2.1 Soil Sampling 52

4.2.2 Particle Sieve Distribution 52

4.2.3 Particle Size Analyzer 53

4.2.4 Specific Gravity 54

4.2.5 Atterberg Limit 55

4.2.6 Standard Proctor Test 57

4.2.7 Shear Strength 58

4.3 Coconut Coir Blanket Analysis 61

4.3.1 Tensile Strength 61

4.3.2 Direct Shear 63

4.4. Rainfall on Slope Model Simulation Testing 65

4.4.1 Control Sample with Signal Grass Vegetation 65

for Slope of 00


for Slope of 100


for Slope of 201


for Slope of 30°


for Slope of 40°

xi


for Slope of 50°

4.4.7 Control Sample with Japanese Millet 71

Vegetation for Slope of 00






Vegetation for Slope of 30°





4.4.13 Slope Model with Signal Grass Vegetation 77

and Coconut Coir Blanket for Slope of 00




and Coconut Coir Blanket for Slope of 20°







4.4.19 Slope Model with Japanese Millet 83

Vegetation and Coconut Coir Blanket for

Slope of 0°

xli



Slope of 100

4.4.2 1 Slope Model with Japanese Millet 85


Slope of 20°



Slope of 30°



Slope of 40°



Slope of 500

4.4.25 Controlled Slope Model with Signal Grass 91

Vegetation against Controlled Slope Model

with Japanese Millet Vegetation

4.4.26 Protected Slope Model with Signal Grass 92

Vegetation against Protected Slope Model

with Japanese Millet Vegetation

4.4.27 Controlled Slope Model with Signal Grass 93

Vegetation against Protected Slope Model

with Signal Grass Vegetation

4.4.28 Controlled Slope Model with Japanese 94

Millet Vegetation against Protected Slope

Model with Japanese Millet Vegetation

4.5 Factors Affecting Results 96

4.5.1 Ambience Factor 96

4.5.2 Time Factor 96

4.5.3 Procedures Factor 96

XIII

5 CONCLUSION AND RECOMMENDATIONS

5.1 introduction 99

5.2 Conclusion 100

5.2 Recommendations 102

REFERENCES 104

APPENDIX A log

APPENDIX B 113

APPENDIX C 115

APPENDIX D 117

APPENDIX E 120

APPENDIX F 124

APPENDIX G 128

APPENDIX H 134

APPENDIX 1 143

LIST OF FIGURES

FIGURE NO. TITLE PAGE

2.1 Erosion control blankets for soil slope stabilization 19

2.2 Coconut layers 20

2.3 Original topography and design profiles 28

2.4 Front View of Failed Slope 28

2.5 Interpreted subsoil weathering profile 30

3.1 Flow chart for the sequences of methodology 32

3.2 Sieve set 35

3.3 Particle size analyzer 36

3.4 Density bottle and specific gravity apparatus 37

3.5 Atterberg limit stages diagram 42

3.6 Cone penetration apparatus 42

3.7 Standard proctor apparatus 44

3.8 Compression device 46

3.9 Coconut coir blanket 47

4.1 Particle size distribution curve 53

4.2 Particle size analyzer curve 54

4.3 Liquid limit determination 56

4.4 Graph of dry unit weight against moisture content 57 4.5 Triaxial compression test result for soil sample BHI 59

4.6 Triaxial compression test result for soil sample BHI2 60 4.7 Triaxial compression test result for soil sample B143 60 4.8 Coconut coir blanket was tested on tensile strength machine 61

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49 Tensile Strength graph 62

4.10 Soil sample with coconut coir blanket after shear test 63

4.11 Shear strength linear graph 64

4.12 Rate of Sedimentation for Control Sample with Signal 65

Grass Vegetation for Slope of 00




Grass Vegetation for Slope of 20°







4.18 Rate of Sedimentation Graph for Control Sample with 71

Japanese Millet Vegetation for Slope of 0°


Japanese Millet Vegetation for Slope of 100







4.23 Slope failure 76 4.24 Rate of Sedimentation Graph for Slope Model with Signal 77

Grass Vegetation and Coconut Coir Blanket for Slope of 00

4.25 Rate of Sedimentation Graph for Slope Model with Signal 78

Grass Vegetation and Coconut Coir Blanket for Slope of 100


Grass Vegetation and Coconut Coir Blanket for Slope of

200



300



40°



50°

4.30 Rate of Sedimentation Graph for Slope Model with 83

Japanese Millet Vegetation and Coconut Coir Blanket for

Slope of 0°



Slope of 10°



Slope of 20°



Slope of 30°



Slope of 40°

4.35 High amount of collection in TSS for every 10 minutes 88 4.36 The collection decreased for every 10 minutes 89 4.37 Rate of Sedimentation Graph for Slope Model with 90


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xvii

Slope of 500

4.38 The comparison of Type of Grass in TSS for Controlled 91

Slope

439 The comparison of Type of Grass in TSS for Protected 92

Slope

4.40 The comparison of Type of Slope Protection using the same 93

Vegetation in TSS

4.41 The comparison of Type of Vegetation using the same 94

Slope Protection in TSS

5.1 Total Suspended Solids against Degree of Slope for all the 100

Slope Model

xv"

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Physical properties of coir fibre 22

2.2 Fabric categories 22

2.3 Interpreted shear strength parameters 29

4.1 Data of specific gravity testing 55

4.2 Shear strength parameters 58

LIST OF SYMBOLS AND ABBREVIATIONS

A - Soil loss in tons/acre/year

R - Rain factor

K - Soil erodibility

LS - Topographic factor

C - Cover factor

P - Practice factor

c - Soil cohesion

E - Young's Modulus

v - Poisson's ratio

c' - Effective cohesion

(1)0 - Effective friction angle

LL - Liquid limit

PL - Plastic limit

SL - Shrinkage limit

Su - Undrained shear strength

AL - Length deformation

L0 - Initial length

- Strain

Gs - Specific gravity

7 - Dry unit weight

Cu - Shear strength

% - Percentage

Rm - Micrometer

- Degree

mic - Micron

xix

w% - Water content

M0 - Initial mass

G - Stress

MD - Machine direction

CD - Cross direction

lbs - Pounds

in - Inch

ac - Acre

tan - Tangent

f - Internal friction

kPa - Kilo Pascal

- Degree Celcius

ASTM - American Society for Testing and Materials

AASHTO - American Association of State Highway and Transportation

Officials

LIST OF APPENDICES

APPENDIX TITLE PAGE

A Soil Classification 108

B Specific Gravity 113

C Atterberg Limit 115

D Standard Proctor 117

E Shear Strength 120

F Tensile Test 124

G Direct Shear 128

H Total Suspended Solids 134

I Comparison of Results 143

wi

CHAPTER 1

INTRODUCTION

1.1 Background of Research

The surface of planet earth consists of mountains, flat grounds and water

filled sea. Each of these places needs to play roles in locating developments as the

world has limited ground areas for all mankind to live in. As these places are built up

to meet advanced civilization, the nature on their own is changing. The ground

surface of earth basically is having crust movement as the planet rotates on its axis.

The ambience which lives in the atmosphere too becomes the factors which lead to

the adjustment of nature physically. Thereafter, the geological cycle of earth may be

classified as disturbed.

Geologically, Malaysia is greatly disturbed by one of the major natural

disaster which is landslide. Landslide occurs mostly at the surface of mountainous

slopes that engaging danger to the residents. This alarming phenomenon can be

predicted by geologists but on many cases, it happens unexpectedly leaving the

residents in chaos. Lives are taken away and private properties are damaged which

concurrently affect the residents spiritually and the country's economic sustainment.

Many cases involved in the previous years and now seems like there is very minor

improvement has been implemented in slope reinforcement due to the numerous agendas.

2

In Peninsular Malaysia, the states located in the region of north, west and

south are having the gradual and evenly distributed rainfall season throughout the

month of April to May and September to December,. These States comprising of

Kedah, Perak, Selangor and Johor are slightly affected to the landslide occurrence as

a result from heavy rainfall. Based On climatology, these places basically have a dry

season starting from January. Due to this, they are least in the dilemma of landslide.

Out of jurisdiction, flooding may occur from time to time in the raining season.

Apparently, landslide which takes place due to human activities is normally

because of major construction on the existing site. Construction works such as the

cuts and excavations, removal of retaining wall or sheet piles and drawdown of water

bodies can easily take leads to slope failure. Certain construction uses high

technologies in order to cut hill slopes. Explosive are one of the major practice and

most expensive method which being carried out. Any misleading of the explosion

could simply produce unnecessary vibrations to the slope area.

Another example of human activities effects will be mining and quarrying

process for the purpose of construction materials trading and entrepreneurship.

Underprivileged monitoring of these activities might cause the area of site to be

exposed for landslide. Additionally, the construction for tunnel without proper soil

investigation and effective work may contribute in slope failure too. The hill that has

been drilled may be subjected to undesired settlement. More to this construction

industry, the building of a damn have a major risk in developing a landslide. Water

which run underneath the ground level and water pressure against the wall of the

dam may create a downfall.

Due to poor site investigation, a critical landslide may sweep off the entire

construction area. This may happen too to completed projects for example in

Malaysia itself, Jalan Semantan and Bukit Antarabangsa had landslide particularly in

2008 which killed a number of residents. Both projects are residential areas which

stand aside to a retaining wall that protects the slope from settling down. These two

cases were most likely the repetition of previous Highland Tower collapse back in 1985. It was a massive destruction as the whole tower fell to the side leaving few

3

survivors. It is learnt that, construction within slope areas is Still unsecured due to

natural effects not human errors.

Though high technology and recognized philosophies had been practiced into

the matter of slope protection, flaws seemed to rise and slowly engaging total

disaster. Effort on improving of the reinforcement to slope have to be revised

continuously as the analogy changes because of the transition made to the

environment naturally or man-made. As the deformation keeps going on, slope

erosion occurs because of the soil which eroded by water and wind factor. The slope

erosion is one major reason why landslide phenomenon exists. The landslide proved

that better technology is highly recommended for slope embankment and more

protection is seriously needful in order to have a promising Factor of Safety.

1.2 Problem Statement

Soil erosion is one factor why landslide occurs. The erosion involved the

human activities which development is engaged over the existing area. Due to

uncontrollable scenario, the soil surface is exposed to wind and water. As the soil is

being eroded, the changes made to the originality of the soil. Numerous elements are

taken into discussion for the basic properties of the soil are altered. The soil will be

losing nutrients and moisture, change in its structure and vegetation, and running

through a salirnzation. Hence, the behaviour of the soil is deformed form its original

state leaving it ineligible for many purposes.

Once an area of soil becomes degraded and eroded, the particular area shall

be put up for sale as it cannot be used for farmland anymore. The elements of the soil

which are altered made the soil become unsuitable for plantation to grow especially

at highland grounds. The maintenance fee may go higher as the soil has to be

modified in order to regain its natural behaviour. Unfortunately, the value of the soil

too will decrease therefore the people fanning it would be harvesting lesser or

4

reducing stock and eventually end up poorer. Regarding to this, it can be assumed

that erosion causes social, economic and political consequences to farm industries.

Whenever there is any presence of soil erosion, the existing ground is no

longer safe for construction unless remedial measures are implemented. In residential

divisions, high value residential nowadays favours the location of highland grounds

that overlook scenic environment. However, the safety measures promised are

vulnerable as any changes made by Mother Nature are unpredictable. Most eases that

relates to residential happens when the slopes holding the houses overturn and slide

resulting the houses to collapse. Lives were taken at stake. A home which is the

safest area for people to live in becomes dangerous unexpectedly.

Other than residential area, high rise building such as offices, academic

institutions, private organizations are too exposed to landslide caused by soil erosion.

These multi-storeys building faces higher risk of destruction if the foundation of the

structure is disrupted by the soil erosion scenario. The foundation which holds the

main structure of the building may fail and bring down the whole building. Many

cases have been highlighted in previous years as soil erosion keep on occurring after

intense improvement on the slope reinforcement.

Most importantly, roadways which have been the network to human

connections too seemed to be invaded by the severity of slope erosion. Highways

which cut through a hill will be facing the dilemma of soil erosion by both sides of

the excavated hill. The soil erosion which affects the roadway condition will be

hazardous to the road users. Rocks, dust, and soil particles deposited by water

certainly blocks the sight for the drivers. In a worsened scenario, the slope may fail

thoroughly and engaging into landslide. Vehicles on the road during that particular

moment may be having fatal accidents. If the destruction continues and the roadway

itself collapses into lower ground, the structure of the main road is impaired. Road

network is barred and transport connection is limited.

5

Seemingly, slope erosion by means of soil erosion leads to many difficulties

to the nature and its surroundings. Most of the factor is withstood by the human

activities themselves. The failure that damaging farmland, residential areas, high rise

buildings and roadways are the major places involved. Lives are taken and properties

are swept off each time a landslide occurs. As protecting slope is very important, this

study leads to one of the many preventive measures by reinforcing the slope literally.

1.3 Objectives

The objectives of the study are:

1. To determine the strength and durability of coconut coir matting.

2. To determine the effectiveness of the coir blanket in controlling slope

erosion.

6

1.4 Scope of Study

In the real world, the phenomenon of landslide cannot be forecasted of its

time of occurring and how bad it is going to be. Many factors affected the movement

of particles in the soil layers which were clearly subjective. The safety protections

suggested and applied too were occasionally vulnerable due to the changes made by

the Mother Nature. To gain such safety protections, many measures were taken into

consideration. Due to this, testing was carried out based on the objectives of this

study. The effectiveness of coconut coir in controlling slope erosion was determined

by several testing.

The related laboratory testing in this study covers in two specific engineering

division. It included both Geotechnical Engineering testing and Structural

Engineering testing. These two majors were mainly for the soil sample analysis and

the coconut coir properties assessment respectively. For Geotechnical Engineering

testing, there were Soil Classification, Atterberg Limit, Specific Gravity, Standard

Proctor, Shear Strength and Direct Shear tests. While Structural Engineering

highlighted on the coconut coir blanket properties assessment based on the Tensile

test.

In this study, a rainfall simulation model was built which contain a sloped

surface of soil sample. An artificial rainfall was spurred all over the soil sample area,

filtered into the layer of soil and the deposited amount of water was collected at the

edge of the model. The rainfall water supplied came from a direct water supply from

a water tab. The rainfall was designed to distribute the water uniformly over the soil

sample area. Sprinklers were installed as to contribute in the distribution of the

artificial rainfall thoroughly. Pressure gauge was connected to the main pipeline of

the water supply for monitoring the water pressure so to alter the intensity of the

rainfall as favoured in the testing. Each testing was gone for a one-hour raining

session. The data accumulated were averaged out over 60 minutes.

7

One controlled condition of slope was to be tested with bare surface. The

other condition was the sloped surfaces covered With coconut coir blanket. Both of

the conditions were varied by the vegetations used which were the Signal Grass and

Japanese Millet. The angles for the slope tested were 0 0, 100, 200, 30°, 40° and 500.

Therefore, the total number of cases was 144. The soil sample was collected from a

coflstrUCtlOfl site in Bukit Gambang, Pahang. Soil which was altered extremely is

most likely being disapproved as the originality of the soil content will be needed to

assure the properties of natural soil.

1.5 Significant of Study

The phenomenon of landslide can be factored by many aspects. There are

ground conditions, geomorphological processes, physical processes and man-made

processes. One of the main factors is erosion that belongs in the category of

geomorphological processes as it is a norm occurrence in Malaysia. Out of the many

factors, erosion is chosen to be discussed in this study in a way that excessive rainfall

season in Malaysia generates the soil particles movement settled in the slope area. It

is without a doubt that the well-known relationship between heavy rainfall and

landslides is the major contributions to slope erosion.

Remediation processes are highly important to slope failures. But practising

such operation is not recognizable as prevention save lives and the human properties

at the first place. Hence, remedial measures are the ones that need to be stressed out

In controlling slope erosion. Geotextile proves that it is effective to reduce erosion in

slopes. However, geosynthetic fibre is a new material which has better advantages

than the polymerized geotextile already has. Coconut coir is the base material

Selected to be used in this study as it certainly belongs in eco-friendly element. A

coconut coir based blanket is fully produced naturally. The raw material used is the

coconut coir alone without any additives.

the effectiveness of coconut coik blanket in

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