Soil stablization using coir

EFFECTS OF COIR FIBER ON
PROPERTIES OF CLAYEY SOIL
MAJOR PROJECT REPORT
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENT
FOR THE AWARD OF THE DEGREE OF
BACHELOR OF TECHNOLOGY
(Civil Engineering)
Submitted By: Under Guidance:
GAURAV SHARDA
Department of Civil Engineering
Guru Nanak Dev Engineering College,
Ludhiana (Punjab)

ACKNOWLEDGEMENT
It is my proud privilege and duty to acknowledge the kind of help and
guidance received from several people in preparation of this report. It
would not have been possible to prepare this report in this form without
their valuable help, cooperation and guidance.
First and foremost, I wish to record my sincere gratitude to the
Management Guru Nanak Dev Engineering College and to , Professor
and Head of Department Civil Engineering, Guru Nanak Dev
Engineering College, Ludhiana for his constant support and
encouragement in preparation of this report and for making available
library and laboratory facilities needed to prepare this report.
I express My sincere gratitude to my guide, Dr, Department of Civil
Engineering, GNDEC, Ludhiana for guiding me in investigations for this
project. The numerous discussions with him were extremely helpful. We
hold him in esteem for guidance, encouragement and inspiration received
from him.

GURU NANAK DEV ENGINEERING COLLEGE
CANDIDATE’S DECLARATION
I hereby certify that the work which is being presented in the minor
project report entitled “EFFECTS OF COIR FIBER ON PROPERTIES
OF CLAYEY SOIL” by “GAURAV SHARDA” in partial fulfillment of
requirements for the award of degree of B. Tech (Civil Engineering)
submitted in the department of civil engineering at Guru Nanak Dev
Engineering College, Ludhiana under PUNJAB TECHNICAL
UNIVERSITY, Jalandhar, is an authentic record of our own work carried
out under the guidance of .The matter presented in this report has not
been submitted by us in any other University/ institute for award of any
degree.
Signature of Student
GAURAV SHARDA
This is to certify that the above statement made by the candidate is
correct to the best of our knowledge.

ABSTRACT
Fiber reinforced soils have become one of the construction materials in
civil engineering. Construction of building and other civil engineering
structures on availability clayey soil is highly risky, on geotechnical
grounds due to poor strength properties of the clayey soil. There may be
the need for soil treatment to improve the engineering properties of soil.
In practice admixtures with fly ash, lime and geo-grids are used
frequently to stabilize soils and improve their strength properties.
Polyester fibers have extensively used in civil engineering applications
for many years. Ease of application and reduction in cost are making this
treatment more popular. The purpose of this investigation is to identify
and quantify the influence of coir fiber on performance of fiber
reinforced soil specimens. In this study, coir fiber mixed with clayey soil
in various proportions (0%, 0.5%, 1.0% and 1.5% by weight of dry
clayey soil) to investigate the relative strength gained in terms of
compaction CBR. The results clearly indicate that 1% coir fiber have
noticeable influence on CBR value of expansive soil. This is because of
composite effect of waste materials, which changes the brittle behavior
of soil to ductile behavior.

LIST OF FIGURES
Title Page No.
Fig. 4.1: Coir Fiber……………………………………………………………………………………………………………10
Fig. 4.2: Distributed soil specimen……………………………………………………………………………………11
Fig. 4.3: Apparatus for Standard Proctor test…………………………………………………………………..13
Fig. 4.4: CBR testing Machine…………………………………………………………………………………………..15
Fig 4.5: UCS Testing Machine……………………………………………………………………………………………16
Fig 5.3: OMC and MDD of soil + 0% Coir Fiber………………………………………………………………….18
Fig 5.4: OMC and MDD OF SOIL +0.50% Coir fiber……………………………………………………………19
Fig 5.5: OMC and MDD of Soil +1.0% Coir Fiber……………………………………………………………….19
Fig 5.6: OMC and MDD of soil + 1.5% Coir Fiber……………………………………………………………..20
Fig 5.7: OMC Variation with Percentage of Coir fiber………………………………………………………21
Fig 5.8: MDD variation with Percentage of Coir fiber………………………………………………………21
Fig 5.9: Stress-Strain curve for Soil +0%Coir Fiber ……………………………………………………………22
Fig 5.10: Stress Strain curve for Soil +0.5% Coir Fiber……………………………………………………….22
Fig 5.13: UCS Variation with Percentage of coir fiber……………………………………………………….24
Fig 5.14 CBR graph for soil – 0% coir fiber………………………………………………………………………..25
Fig 5.15 CBR graph for soil – 0.5% coir fiber……………………………………….…………………………..25
Fig 5.16 CBR graph for soil – 1% coir fiber……………………………………………………………………..26
Fig 5.17 CBR graph for soil – 1.5 % coir fiber………………………………………………………………….26

LIST OF TABLES
Title Page No.
Table 5.1 Physical Properties Of Soil……………………….…………..…………………17
Table 5.2 OMC and MDD of Soil with Coir Fiber…………………………………20
Table 5.3 Variation of UCS with Percentage of Coir Fiber…………………..24
Table 5.4 Variation of CBR with Percentage of Coir Fiber…………………..27

LIST OF SYMBOLS AND ABBREVIATIONS
BIS Bureau of Indian Standards
C Cohesion
CBR California bearing ratio
CF Coir fiber
G Specific gravity
IS Indian standard
KN kilo Newton
LL Liquid Limit
m Meter
MDD Maximum Dry Density
mm Millimeter
OMC Optimum Moisture Content
UCS Unconfined Compressive Strength
w Water content

Table of Contents
Chapter 1.......................................................................................................................................1
INTRODUCTION ........................................................................................................................1
1.1 General....................................................................................................................................1
1.2 Major deposits of soil in India ............................................................................................1
1.3 Soil Stabilization.................................................................................................................2
1.4 Methods of Soil Stabilization..............................................................................................3
1.5 Coir Fiber............................................................................................................................5
LITERATURE REVIEW .............................................................................................................6
2.1 General................................................................................................................................6
2.2 Previous Studies on Coir Fibre ...........................................................................................6
2.3 Concluding Remarks...........................................................................................................8
Chapter 3.......................................................................................................................................9
PROJECT OBJECTIVE ...............................................................................................................9
Chapter 4.....................................................................................................................................10
MATERIALS AND METHODS................................................................................................10
4.1 General..............................................................................................................................10
4.2 Materials Used ..................................................................................................................10
4.3 Methodology.....................................................................................................................11
4.4 Concluding Remarks.........................................................................................................16
Chapter 5.....................................................................................................................................17
RESULTS AND DISCUSSION .................................................................................................17
5.1 General..............................................................................................................................17
5.2 Index Properties ................................................................................................................17
5.3 Results...............................................................................................................................18
Chapter 6.....................................................................................................................................28
Discussion and Conclusion .........................................................................................................28
6.1 General..............................................................................................................................28
6.2 Conclusions.......................................................................................................................28
6.3 Scope of Further Study .....................................................................................................29
Chapter 7.....................................................................................................................................30
References...................................................................................................................................30

1
Chapter 1
INTRODUCTION
1.1 General
Soil is considered as the earth’s uppermost layer especially where plant grows. It occurs
naturally in the universe mainly by rock’s disintegration. It is one of the cheapest and
easily available material for construction purposes but on the other hand its behavior is
quite complex. As it is a naturally occurring material, we cannot predict its behavior
properly in the different conditions. Same type of soil behaves different in two different
conditions. Here the work of Civil Engineer becomes utmost important, who has to
verify the existing soil can withstand the load coming from superstructure or not.
Soft soils such as clayey or silty soil do not have sufficient strength to withstand heavy
loads and hence pavements constructed over such soils are subjected to early
degradation. Earlier practice of replacing soft soil with good quality soils are nowadays
not feasible due to the high cost involved. The method of treating soft soils at the field
itself using additives is called stabilization of soils. In this treatment, the properties of
soil are improved by mechanical or chemical means. Stabilization of soils has been
always an interesting topic to researchers. Over the years, materials have been used for
stabilization of weak soils such as clays. A recent trend is to utilize waste materials for
modifying soft soils. The advantage of using waste materials in construction includes its
low cost involved and a new solution for the waste disposal.
1.2 Major deposits of soil in India
Following are the five major deposits of soil found in India:
1. Alluvial deposit - It is mainly found in northern in India. It is mainly found in
different layers of clay, silt and sand one after the other, each layer’s thickness
varies from place to place and with different conditions.
2. Black cotton soil - It is mainly found in central India and some parts of
southern India. These types of soil support the production of cotton.
3. Laterite soils – These are mainly found in southern and eastern India. When
wet, these types of soil are quite soft. The red colors present in these types of
soil are due to iron oxide.
4. Desert soils – These types of soils are mainly found in parts of Rajasthan and
nearby states. It mainly consists of dune sand in which particle’s size is in the
range of fine sand.

2
5. Marine deposits – These are mainly found near the coast. The shearing strength
of these deposits is quite low. These are also compressed easily. Large amount
of organic matter is present in them.
1.3 Soil Stabilization
1.3.1 Definition
It is the process in which engineering properties of soils are improved to make them
more stable. When we have to construct any structure, it is not always that we would
get the required type of soil. The soil may lack enough strength and stability to
withstand the structure. In such a case we need to stabilize the soil. To improve various
properties of soil, sometimes we may also change the material of the soil. For this we
may add a chemical or a Cementous material to the soil. The prime objective of soil
stabilization is the reduction of permeability and compressibility of soil and to enhance
the shear strength. The properties of soil vary a great deal at different places or in
certain cases even at one place; the success of soil stabilization depends on soil testing.
1.3.2 Principles of soil stabilization
1. Evaluating the soil properties of the area under consideration.
2. Deciding the property of soil which needs to be altered to get the design value
and choose the effective and economical method for stabilization.
3. Designing the stabilized soil mix sample and testing it in the lab for intended
stability and durability values.
1.3.3 Needs and Advantages
 It improves the strength of the soil thus, increasing the soil bearing capacity.
 It is more economical both in terms of cost and energy to increase the bearing
capacity of the soil rather than going for deep foundation.
 It is also used to provide more stability to the soil in slopes or other such places.
 Stabilization improves the workability and the durability of the soil.
 It helps in reducing the soil volume change due to change in temperature or
moisture content.
 Increase soil resistance against liquefaction under dynamic loading conditions.
 Less expensive compared to other reinforcing materials.
 Construction time can be diminished with the use of reinforcement technique.
 Reduce the compressibility of soil.
 More durable as material is non-biodegradable.
 Improves strength, toughness, ductility and stiffness of soil.

3
1.4 Methods of Soil Stabilization
Soil stabilization with cement, bitumen, lime, chemical stabilization, geotextile,
grouting etc. are discussed. It is a method of improving soil properties by blending and
mixing other materials.
1.4.1 Soil Stabilization with Cement
The soil stabilized with cement is known as soil cement. The cementing action is
believed to be the result of chemical reactions of cement with siliceous soil during
hydration reaction. The important factors affecting the soil-cement are nature of soil
content, conditions of mixing, compaction, curing and admixtures used.
The appropriate amounts of cement needed for different types of soils may be as
follows:
 Gravels - 5 to 10%
 Sands – 7 to 12%
 Silts – 12 to 15%
 Clays – 12 to 20%
The quantity of cement for a compressive strength of 25 to 30 kg/cm2
should normally
be sufficient for tropical climate for soil stabilization.
1.4.2 Soil Stabilization using Lime
Slaked lime is very effective in treating heavy plastic clayey soils. Lime may be used
alone or in combination with cement, bitumen or fly ash. Sandy soils can also be
stabilized with these combinations. Lime has been mainly used for stabilizing the road
bases and the subgrade.
Lime changes the nature of the adsorbed layer and provides pozzolanic action.
Plasticity index of highly plastic soils are reduced by the addition of lime with soil.
There is an increase in the optimum water content and a decrease in the maximum
compacted density and he strength and durability of soil increases.
Normally 2 to 8% of lime may be required for coarse grained soils and 5 to 8% of lime
may be required for plastic soils.
1.4.3 Soil Stabilization with Bitumen

4
Asphalts and tars are bituminous materials which are used for stabilization of soil,
generally for pavement construction. Bituminous materials when added to a soil, it
imparts both cohesion and reduced water absorption.
1.4.4 Soil stabilization with chemicals
Soils are stabilized by adding different chemicals. The following chemicals have been
successfully used:
 Calcium chloride
 Sodium chloride
 Sodium silicate
 Polymers
Functions:
 It lowers the optimum water content.
 It causes a small decrease in the strength of soil.
 Its quantity required is about ½ %of the weight of soil.
1.4.5 Soil reinforcement with Fibers
The soil that has discrete elements i.e. fibers which improve the mechanical behavior of
the soil is called fiber reinforced soil. Soil reinforcement by fiber material was
considered an effective soil stabilization method because of its cost effectiveness, easy
adaptability and reproducibility.
Types of Fiber
Natural Fiber- Since the non- renewable sources will extinct one day, the pollution has
overshadowed everything there is need of much eco- friendly and long lasting resource.
The natural fiber reinforcement takes its motivation from plants. The expansion of plant
roots, isolation of plants and their age are some of the determining the performance of
the natural fiber. Various types of natural fibers used in soil reinforcement are:
 Coconut (coir fiber)
 Sisal fiber
 Palm fiber
 Jute
 Bamboo

5
Synthetic fiber:
 Polypropylene fibers (PP)
 Polyester fibers (PET)
 Polyethylene fibers (PE)
 Glass fibers
 Nylon fibers
In the present investigation, COCONUT (COIR) FIBER is used as soil reinforcement
material.
1.5 Coir Fiber
The coir fiber is enough elastic to twist without breaking and it holds a curl as though
permanently waved. The coir fiber can be used in stabilization of soil and thus it can be
effectively disposed off. The inclusion of fibers has significant influence on engineering
behavior of soil-coir mixtures. The addition of randomly distributed coir fiber resulted
in substantially reducing the consolidation settlement of the clay soil. Length of fiber
has an insignificant effect on these soil characteristics. Whereas fiber content proved
more effective. The work has been done on strength deformation behavior of fiber
reinforced soil and it has been established beyond doubt that addition on fiber in soil
improves the overall engineering performance of soil. Fiber mixed with soil is effective
in all types of soil (Sand, Silt and Clay). The main advantage of coir Fiber is that it is
locally available and is very cheap.
Characteristics of coir fiber
 It is strong.
 It is resistant to stretching and shrinkage.
 It is inert to chemicals.
 It is resistant to abrasion.
 It has suitable mechanical properties and also good hydraulic properties.
Soil and fiber reinforcement:
The strength of soil stabilized by fiber generally increases. The strength goes on
increasing with increase in percentage of fiber content upto certain limit. The studies of
mixture of fiber and soil have shown that the addition of fiber to the soil greatly
enhances the compressive strength of soil.

6
Chapter 2
LITERATURE REVIEW
2.1 General
The study is based on the use of coir fiber as a reinforcement in the soil so in order to
conduct the experimental program, various research literature was studied which helped
in the understanding of the behavior of coir fiber with soil. This chapter describes the
previous study which has been done and a brief review of that study has been done.
2.2 Previous Studies on Coir Fibre
Dasaka and Sumesh (2011) reinforced the soil with the coir fiber at various fiber
content and found that with the fiber length of 15 mm, unconfined compressive strength
increases with the increase in the fiber content and the soil shows a ductile behavior
with the addition of the fiber. It was found that peak compressive strength increased up
to the fiber content of 1.5% and after that, the compressive strength does not increase
considerably. From the study, it can be stated that with the increase in the fiber content
the failure would take place slowly and samples behave like ductile material and well-
defined failure surface could not be seen due to increased ductile behavior.
Chaple and Dhatrak (2013) studied effect of coir fiber on bearing capacity and
settlement of footing, with 0.25%, 0.50%, 0.75% and 1% of coir fiber using the
laboratory model test on square footing which were supported on compressible clayey
soil reinforced with coir fiber which were randomly distributed in soil. It was observed
that there is an increase in bearing capacity of soil by coir fiber. The ultimate bearing
capacity for reinforced soil with 0.50% coir for 100 mm, 50 mm and 25 mm depth were
425 kN/m2, 495 kN/m2 and 665 kN/m2 respectively which were quite higher than
unreinforced soil having a value of 250 kN/m2. The bearing capacity increases only up
to a fiber content of 0.50% and there after start decreasing with the further addition of
coir fiber in it.

7
Singh and Mittal (2014) investigated the clayey soil with varying the percentages of
coir fiber as 0.25%, 0.50%, 0.75% and 1% by weight. A series of unconfined
compression test (UCS) and California bearing ratio (CBR) test were conducted in his
study. From the study, it was found that there is considerable improvement in
compressive strength of the soil reinforced with the coir fiber. Soil with no
reinforcement had an unconfined strength of 2.75 kg/cm2 which then on adding of fiber
increased to a value of 6.33 kg/cm2 for coir content of 1% by weight of soil, this
increase in value could be because of increase in the shear parameters, it was found
difficult to prepare the identical sample beyond 1% of fiber content so, only up to 1% of
coir fiber was used in his study. From the CBR tests also it can be stated that the value
for both the unsoaked as well as the soaked test has considerably increased on
increasing the fiber content in the soil sample, it was noted that the soaked value of
CBR has improved to a value of 9.22% from that of 4.75% when 1% coir fiber was
included in the soil and also for the unsoaked condition the value has increased from
8.22% to 13.55%. It could be concluded from his study that coir fiber can be utilized
successfully in sub base for flexible pavement and also for the rigid pavement.
Das et al. (2016) studied about the shear strength parameters of the unreinforced and
reinforced soil with coir fiber. A series of direct shear test were conducted at the normal
stress of 0.5 kg/cm2, 1.0 kg/cm2 and 1.5 kg/cm2. The coir fiber was added to the value
of 1%, 2% and 3% by weight of soil. It was observed that the application of coir fibre
on sand result in an increase in the shear strength parameters. The main cause for the
improved shear strength is that in the absence of reinforcement the soil shows brittle
failure but after the reinforcement, the soil starts showing the ductile failure as the
friction has now been developed between the soil and the reinforced material. It was
also seen that increase of the shear strength parameters was only up to the optimum
value of fibre content which here comes out to be 2.1%, beyond this the reduction in the
internal friction angle is obtained and hence in the shear strength of the soil.
A.Anandhamurugan and K Karuppasamy (2017) improvement of CBR values for
the effect of cement and randomly distributed Coir Fiber separately and combination of

8
both. It was observed that the addition of cement increased the CBR of the soil and it is
increased with every percentage addition of cement and CBR value of 10% is achieved
for 1.5% addition of cement to total volume. The results clearly indicate that 1.5%
cement and 0.5%coir fiber have noticeable influence on CBR value of expansive soil.
Pooja Upathyay and Yatendra Singh (2017) studied effect of coir fiber on shear
strength of soil by carrying out direct shear test and unconfined compression test on two
different samples. It was observed that with fiber reinforcement of 0.5%,1.0% and 1.5%
the increase in cohesion was found to be 10%, 4.8% and 3.73% respectively and the
increase in the angle of internal friction was found to be 0.8%, 0.31% and 0.47%
respectively. Overall it can be concluded that reinforcing soil with fibers can be
considered ad good ground improvement technique especially in engineering projects
on weak soils where it can act as a substitute to deep/raft foundation, reducing the cost
of project.
Ayininuola and Oladotun (2016) investigated the geotechnical properties of soil when
mixed with coir fiber. Coir with the percentages varying from 0.1 to 1.5% was used and
three different soil samples were used to carry out the experimental work. Cohesion
values of soil samples increased up to the fiber content of 1.2% and after this fiber
content it starts decreasing and the angle of internal friction also increased up to the
same fiber content, for the CBR tests on all three soil samples the strength increased up
to 1.2% of coir fiber after this value it starts decreasing so making 1.2% of coir fiber as
the optimum dose to be mixed in soil.
2.3 Concluding Remarks
This chapter has shed some light on the previous studies on the coir fiber soil mixture.
It showed the variation of different geotechnical properties of soil mixed with coir fiber
as reported by many researchers.

9
Chapter 3
PROJECT OBJECTIVE
1. To study the various geotechnical properties of soil such as maximum dry
density, optimum moisture content, California bearing ratio and unconfined
compressive strength parameters by mixing soil with different percentages of
coir fiber.
2. To suggest an optimum content of coir fiber to be mixed in the soil for strength
improvement in the soil.

10
Chapter 4
MATERIALS AND METHODS
4.1 General
The main objective of this study is to investigate the change in the behaviour of soil
when coir fibre at varying percentages was mixed in clayey soil through the various
geotechnical tests conducted in the laboratory.
4.2 Materials Used
4.2.1 Coir Fiber
Coir fiber was purchased from local market in Phagwara, District Kapurthala (Punjab).
Coir used for the study was cut into average length of 30mm to 50mm. Fig. 4.1 shows
the coir fiber used for the study.
Fig. 4.1 Coir Fiber

11
4.2.2 Soil
The soil used in the study was taken from Geotechnical Laboratory in Guru Nanak Dev
Engineering College, Ludhiana). As per Indian Standard, the soil is classified as CL-
ML. Soil used for the study is shown in Fig. 4.2.
Fig. 4.2 Distributed soil specimen
4.3 Methodology
The clayey soil was mixed with four different content of coir fibres which were
0.50%, 1% and 1.5% in order to prepare various samples.
In Order to investigate the various geotechnical properties of soil tests were
conducted in soil and soil mixed with the various percentages of coir fibre, the
various tests conducted are listed as:
 Grain size distribution
 Consistency limits
 Specific gravity
 Compaction test

12
 Unconfined compression test
 California bearing ratio test
A brief discussion about these tests is presented in the following sections.
4.3.1 Determination of Grain Size Distribution
In order to determine the content of coarse grain soil and fine grain soil this test was
conducted in two steps:
 Sieve analysis
 Sedimentation analysis
Sieving was done to determine the coarser content of the soil which determines gravel
and sand proportion in the soil sample. This was done by using various sieves ranging
from 4.75 mm sieve size to .075 mm as per IS: 2720 (Part IV) -1985.
4.3.2 Determination of Consistency Limits
To determine the Liquid limit, Plastic limit of soil tests was conducted with reference to
IS: 2720 (Part V)-1985.Liquid limit is the minimum water content at which soil has a
tendency to flow and all soil possess a negligible shear strength at the liquid limit, it is
performed with the help of Casagrande’s apparatus in the lab. Plastic limit refers to that
water content at which soil sample would just begin to crumble when rolled into a
thread of approximately of 3 mm in diameter. Plasticity index is the range of moisture
content over which a soil exhibits plasticity. It is equal to the difference of liquid limit
and plastic limit.
4.3.3 Specific Gravity Determination
Specific Gravity was determined by soil fraction passing through 4.75 mm IS sieve with
the help of Pycnometer as per instruction of IS: 2720 (Part III) 1980. It is defined as the

13
ratio of the weight of a given volume of solids to the weight of the equivalent volume of
water at 4°C.
4.3.4 Procedure for Standard Proctor Compaction Test
To analyses the geotechnical properties of soil like unconfined compressive strength,
CBR value of soil, we need to find out the water content at which with the help of
compactive effort we can find the maximum value of dry density, referring this water
content to be as optimum moisture content (OMC) and dry density as maximum dry
density (MDD) and in order to determine these values standard proctor tests were
conducted in the lab with a help Cylindrical mould of 1000 cc capacity with 100 mm of
diameter and 127.3 mm height fitted with detachable base and collar with 50 mm height
was used. The soil was compacted in 3 layers each receiving 25 number of blows from
a rammer of weight 2.6 kg falling from a height of 310 mm. Fig. 4.3 shows the sample
of mould in which compaction is done.

14
Fig. 4.3 Apparatus for Standard Proctar test
4.3.5 Procedure for California Bearing Ratio Test
It is the ratio of test load with standard load represented in percentage for a given
penetration of plunger with a combination of load penetration and empirical chart this
method allow us to determine the thickness of pavement. To investigate the effect of
coir fiber in enhancing the CBR value of soil California bearing ratio test in unsoaked
condition was conducted in accordance with IS 2720 (Part XVI)-1987 on a soil
compacted to their MDD at OMC in a mould of diameter 150mm and height of 175 mm
provided with a 50 mm height collar and a displace disc of 50 mm deep to keep in
mould during penetration, a surcharge is also kept to stimulate the effect of overlying
pavement. Penetration of plunger of 50 mm in diameter is allowed with a rate of 1.25
mmmin and load reading at various interval are noted down. CBR values are calculated
for penetration of 2.5 mm and 5 mm for unsoaked CBR result are produced
immediately. Fig. 4.4 shows the CBR machine used in the study.

15
Fig. 4.4 CBR testing Machine
4.3.6 Procedure for Unconfined Compressive Strength Test
In order to determine the shear strength of soil, it is one of the fastest and easy to
perform test which widely used for cohesive soil. To study the effects of coir fibre in
strength behaviour of soil unconfined compression test were performed in accordance
with IS: 2720 (Part X) – 1991.
The cylindrical test specimens were prepared from a mould of size 50 mm (diameter) X
100 mm (height). For strength determination samples were put in compression testing
machine and a load was applied on it with a strain rate of 1.25 mm per minute until
either the sample fails by cracking or strain in the sample is more than 20% of the
length of the sample. The unconfined compressive strength of specimens was
determined from stress versus strain curves. Fig. 4.5 represent the UCS testing machine.

16
Fig 4.5 UCS Testing Machine
4.4 Concluding Remarks
The experimental programme, as discussed in this chapter is carried out in view of the
objectives of the study. The results obtained by conducting different types of tests on
the soil and soil mixed with different percentages of coir fiber are presented and
analyzed in the next chapter.

17
Chapter 5
RESULTS AND DISCUSSION
5.1 General
A series of conventional laboratory tests including standard compaction tests, California
bearing ratio tests, unconfined compressive strength tests were carried out on the soil
mixed with different percentages of coir fiber. The tests results and discussion are
presented in this chapter.
5.2 Index Properties
5.2.1 Specific Gravity
Specific Gravity is one of the vital properties required for geotechnical and different
applications of soil. The specific gravity of soil was determined according to IS: 2720
(Part III/Sec II) 1980. An average of three sample is accounted. The Specific gravity of
the soil sample is found to be 2.65.
5.2.2 Consistency Limits
The tests for consistency limits were conducted as per IS: 2720 (Part V) 1985. From the
Fig. 5.2, the liquid limit of soil was observed as 26.5%. Plastic limit of the soil sample
was 21%. So, plasticity index (PI) of soil was 5.5%
Parameter Value
Specific gravity(G) 2.65
Liquid Limit 26.5
Plastic Limit 21
Plasticity Index 5.5
Optimum Moisture Content (OMC)% 11

18
Dry Density, KN/m3
17.82
CBR Percentage 1.24
Soil Type CL-ML
Unconfined Compressive Strength .335 kg/cm2
Table 5.1 Physical Properties of Soil
5.3 Results
The compaction tests were done on soil without coir fibre and with the varying content
of coir fiber, the results of the various tests conducted are shown in Figs. 5.3 to 5.6
Fig 5.3 OMC and MDD of soil + 0% Coir Fiber
17.33
17.79
17.67
17.33
16.74
16.6
16.8
17
17.2
17.4
17.6
17.8
18
0 2 4 6 8 10 12 14 16 18
MaxdryDensity(KN/m3)
Water Content (%)

19
Fig 5.4 OMC and MDD OF SOIL +0.50% Coir fiber
Fig 5.5: OMC and MDD of Soil +1.0% Coir Fiber
14.19
15.98
16.28
16.51
16.33
15.93
14
14.5
15
15.5
16
16.5
17
0 5 10 15 20
MaxDryDensity(KN/m3)
Water Content (%)
15.76
16.91
17.08
16.96
16.53 16.5
15.6
15.8
16
16.2
16.4
16.6
16.8
17
17.2
0 2 4 6 8 10 12 14 16 18 20
Water Content (%)

20
Fig 5.6: OMC and MDD of soil + 1.5% Coir Fiber
5.3.1 Summary of Results
The compaction tests were performed using soil with varying proportion of coir fiber.
The results obtained for each mix are summarized in Table 5.2.
S.NO. Material OMC (%) MDD (KN/m3
)
1 Soil+ 0.00%Coir Fiber 11 17.82
2 Soil+ 0.50%Coir Fiber 12.2 17.08
3 Soil+ 1.00%Coir Fiber 14 16.51
4 Soil+ 1.50%Coir Fiber 14.6 14.60
Table 5.2 OMC and MDD of Soil with Coir Fiber
13.02
14.22
14.58
14.51
14.27
13.98
12.8
13
13.2
13.4
13.6
13.8
14
14.2
14.4
14.6
14.8
0 5 10 15 20 25
Water Content (%)

21
Fig 5.7 OMC Variation with Percentage of Coir fiber
Fig 5.8 MDD variation with Percentage of Coir fiber
11
12.2
14
14.6
0
2
4
6
8
10
12
14
16
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
OMC(%)
Percentage of Coir Fiber (%)
17.82
17.02
16.51
14.6
0
2
4
6
8
10
12
14
16
18
20
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
Percentage of Coir Fiber (%)

22
5.3.2 Results of Unconfined Compressive Strength Tests
The unconfined compressive strength tests were performed on soil and soil reinforced
with coir fiber. The stress–strain behaviour obtained during the unconfined compression
tests are shown in the upcoming plots.
Fig 5.9: Stress-Strain curve for Soil +0%Coir Fibe
Fig 5.10: Stress Strain curve for Soil +0.5% Coir Fiber
0
0.022
0.039
0.061
0.09
0.155
0.237
0.267
0.316
0.335
0.322
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07
Stress(kg/cm2)
Strain
0
0.027
0.081
0.133
0.17
0.215
0.246
0.271
0.295
0.318
0.331
0.345 0.352
0.335
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16
Stress(kg/cm2)
Strain

23
From figs 5.5 to 5.8 It was observed that the UCS of soil was found to be 0.335, 0.352,
0.374, 0.428 kg/cm2
.
0
0.026
0.088
0.162
0.246
0.288
0.312
0.331
0.348
0.361
0.374 0.367
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18
Stress(kg/cm2)
Strain
0
0.054
0.118
0.157
0.198
0.225
0.265
0.301
0.335
0.365
0.399
0.428
0.412
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.1 0.2 0.3 0.4 0.5
Stress(kg/cm2)
Strain

24
5.3.3.1 Summary of Results
UCS tests were performed using soil with varying proportion of coir fiber. The results
obtained for different mixes are summarized in Table 5.4.
Coir Fiber (%) Strength (kg/cm2
)
0.00 0.335
0.5 0.352
1.0 0.374
1.5 0.428
Table 5.3 Variation of UCS with Percentage of Coir Fiber
Fig 5.13 UCS Variation with Percentage of coir fiber
0.335
0.352
0.374
0.428
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6
AxisTitle
Axis Title

25
5.3.3 Results of California Bearing Ratio Test
Fig 5.14 CBR graph for soil – 0% coir fibre
F ig
5.15 CBR graph for soil – 0.5% coir fibre

26
Fig 5.16 CBR graph for soil – 1% coir fibre
Fig 5.17 CBR graph for soil – 1.5 % coir fibre

27
Coir Fiber (%) CBR Value
0 1.24
0.5 1.95
1 2.68
1.5 2.55
Table 5.4 Variation of CBR with Percentage of Coir Fiber
Concluding Remarks
The results obtained by conducting different types of tests on the soil and soil mixed
with different percentages of coir fiber are discussed in this chapter. The conclusions
drawn from the results as discussed above are presented in the next chapter.
*

28
Chapter 6
Discussion and Conclusion
6.1 General
The study was undertaken to investigate the influence of coir fibre in the soil. Tests
were performed to evaluate MDD and OMC relationships, UCS and CBR values of soil
with different proportions of coir fibre. The results of the tests conducted are presented
and discussed in the previous chapter.
6.2 Conclusions
On the basis of present experiment study, the following conclusions are drawn.
Proctor Test Results.
a) Maximum Dry Density is decreasing with increase in percentages of Coir fibre.
The value has decreased from 17.82 KN/m3 to 14.60 KN/m3.
b) The percentage of Coir fibre ranging from 0.25 % to 1 % mixed to the soil is
responsible for the decrement of Maximum Dry Density.
c) Optimum Moisture Content increased from 11 % to 14.6 % with increase in the
percentage of coir fibre to the soil.
Unconfined Compressive Strength Test
a) Unconfined compression strength test conducted at different percentages of coir
fiber.

29
b) As the percentage of Coir fibre increases to the soil, the unconfined compression
strength increased up to coir content of 1.5%.
c) The Optimum percentage of Coir fibre mixed to soil was found 1.0% after
conducting a series of a laboratory test.
d) The Unconfined Compressive Strength increases from 0.335 Kg/cm2
to 0.428
Kg/cm2
California Bearing Ratio Test Result
a) The CBR value increases from 1.24 to 2.68.
b) The optimim value of fibre was found to be 1% in which CBR value increased
by 2.16 times the CBR value of virgin soil.
6.3 Scope of Further Study
 Coir fibre is the waste material obtained from the husk of coconut fruit and can
be used for civil engineering constructions.
 Stone dust, fly ash and rice husk etc. other additives can be used in mix with
Coir fibre to improve strength of soil.
 Coating of coir fibre can be done to increase the life of fibre.
 A study on compressibility and consolidation characteristics of soil mixed with
coir fibre is suggested and aspects of bearing capacity also warrant further
investigation.

30
Chapter 7
References
1. Dasaka, S. M., & Sumesh, K. S. (2011). Effect of coir fiber on the stress–strain
behavior of a reconstituted fine-grained soil. Journal of Natural Fibers, 8(3),
189-204.
2. Chaple, P. M., & Dhatrak, A. I. (2013). Performance of coir fiber reinforced
clayey soil. The International Journal of Engineering and Science, 2(4), 54-64.
3. Upadhyay, P., & Singh, Y. (2017). SOIL STABILIZATION USING
NATURAL FIBER COIR.
4. Ayininuola, G. M., & Oladotun, P. O. (2016). Geotechnical properties of
coconut coir fiber soil mixture. Journal of Civil Engineering Research, 6(4), 79-
85.
5. Hejazi, S. M., Sheikhzadeh, M., Abtahi, S. M., & Zadhoush, A. (2012). A
simple review of soil reinforcement by using natural and synthetic fibers.
Construction and building materials, 30, 100-116.
6. Chauhan, M. S., Mittal, S., & Mohanty, B. (2008). Performance evaluation of
silty sand subgrade reinforced with fly ash and fibre. Geotextiles and
geomembranes, 26(5), 429-435.
7. Prabakar, J., & Sridhar, R. S. (2002). Effect of random inclusion of sisal fibre on
strength behaviour of soil. Construction and Building Materials, 16(2), 123-131.
8. Dr. K.R. Arora ,”Soil mechanics and foundation engineering”, S.Chand and
company limited, New delhi,2010.
9. IS:2720, (Part 5) Indian standard code of practice for determination of liquid
and plastic limit.
10. IS:2720, (Part 7) Indian standard code for practice for determination of water
content- Dry density relation using light compaction.
11. IS:2720, (Part 10) Indian standard code of practice for determination of
unconfined compressive strength.
12. IS:2720, (Part 16) Indian standard code of practice for determination of CBR.

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