STRENGTH CHARACTERISTICS OF RANDOMLY DISTRIBUTED … · When added to the fibre reinforcements in...
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International Journal of Civil Engineering and Technology (IJCIET)Volume 8, Issue 5, May 2017, pp.
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ISSN Print: 0976-6308 and ISSN Online: 0976
© IAEME Publication
STRENGTH CHARACTERISTICS OF
RANDOMLY DISTRIBUTED COCONUT COIR
REINFORCED LITHOMARGIC CLAY
Professor, Department of Civil Engineering, MIT, Manipal University, Manipal
Asst. Professor, Department of Civil Engineering,
Aayush Sharma
Final year B.Tech students, Department of Civil Engineering, MIT, Manipal University,
ABSTRACT
The Lithomargic Clay is a
Konkan belt of South India. The problematic soil loses its strength under wet
conditions and tends to flow with the water leading to the formation of cavities and
unsettlements. Thus, proving the soil to be highly unstable for heavy
work and since the construction on this soil is unavoidable, there is an immediate
need for detailed investigations to improve
increase the strength parameters of the locally available Lithomargic clay by
reinforcing it with randomly distributed untreated coconut coir fibres and then by
adding a coating of Cashew Nut Shell Liquid Oil, a commonly used industrial
disinfectant, on the fibres to improve its durability. The study focused on the proposal
of only locally available material, to provide an economical and efficient solution to
the problem. It was observed that with the inclusion of coir fibres, the strength
parameters of the soil improved, with the cohesion of the soil increasing by almost
five times when reinforced with untreated randomly distributed coir fibres and by six
times when a coat of CSNL Oil was applied to the fibres.
Key words: Stabilisation,
oil (CNSL).
Cite this Article: Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma,
RaginiGogoi and SagarMadhukar Strength Characteristics of Randomly Distributed
Coconut Coir Reinforced L
Engineering and Technology
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International Journal of Civil Engineering and Technology (IJCIET) 2017, pp. 1122–1134, Article ID: IJCIET_08_05_119
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6308 and ISSN Online: 0976-6316
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STRENGTH CHARACTERISTICS OF
RANDOMLY DISTRIBUTED COCONUT COIR
REINFORCED LITHOMARGIC CLAY
Purushotham G. Sarvade
Professor, Department of Civil Engineering, MIT, Manipal University, Manipal
Deepak Nayak
Asst. Professor, Department of Civil Engineering, MIT, Manipal University, Manipal
Aayush Sharma, RaginiGogoi and SagarMadhukar
Final year B.Tech students, Department of Civil Engineering, MIT, Manipal University,
Manipal.
Lithomargic Clay is an abundantly available soil type in the high rainfall
Konkan belt of South India. The problematic soil loses its strength under wet
conditions and tends to flow with the water leading to the formation of cavities and
unsettlements. Thus, proving the soil to be highly unstable for heavy
work and since the construction on this soil is unavoidable, there is an immediate
need for detailed investigations to improve its stabilisation. The paper aims to
increase the strength parameters of the locally available Lithomargic clay by
einforcing it with randomly distributed untreated coconut coir fibres and then by
adding a coating of Cashew Nut Shell Liquid Oil, a commonly used industrial
disinfectant, on the fibres to improve its durability. The study focused on the proposal
ocally available material, to provide an economical and efficient solution to
the problem. It was observed that with the inclusion of coir fibres, the strength
parameters of the soil improved, with the cohesion of the soil increasing by almost
hen reinforced with untreated randomly distributed coir fibres and by six
times when a coat of CSNL Oil was applied to the fibres.
, Randomly distributed coir fibres, Cashew nut shell liquid
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma,
RaginiGogoi and SagarMadhukar Strength Characteristics of Randomly Distributed
Coconut Coir Reinforced Lithomargic Clay. International Journal of Civil
Engineering and Technology, 8(5), 2017, pp. 1122–1134.
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=5
asp?JType=IJCIET&VType=8&IType=5
STRENGTH CHARACTERISTICS OF
RANDOMLY DISTRIBUTED COCONUT COIR
REINFORCED LITHOMARGIC CLAY
Professor, Department of Civil Engineering, MIT, Manipal University, Manipal.
MIT, Manipal University, Manipal.
SagarMadhukar
Final year B.Tech students, Department of Civil Engineering, MIT, Manipal University,
e in the high rainfall
Konkan belt of South India. The problematic soil loses its strength under wet
conditions and tends to flow with the water leading to the formation of cavities and
unsettlements. Thus, proving the soil to be highly unstable for heavy construction
work and since the construction on this soil is unavoidable, there is an immediate
stabilisation. The paper aims to
increase the strength parameters of the locally available Lithomargic clay by
einforcing it with randomly distributed untreated coconut coir fibres and then by
adding a coating of Cashew Nut Shell Liquid Oil, a commonly used industrial
disinfectant, on the fibres to improve its durability. The study focused on the proposal
ocally available material, to provide an economical and efficient solution to
the problem. It was observed that with the inclusion of coir fibres, the strength
parameters of the soil improved, with the cohesion of the soil increasing by almost
hen reinforced with untreated randomly distributed coir fibres and by six
Randomly distributed coir fibres, Cashew nut shell liquid
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma,
RaginiGogoi and SagarMadhukar Strength Characteristics of Randomly Distributed
International Journal of Civil
http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=8&IType=5
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
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1. INTRODUCTION
Manipal is a small educational suburb of the city of Udupi in Coastal Karnataka, South India.
A rise in its population and fast growing industries in the adjoining areas of Mangalore and
Udupi has exposed this placid town to rapid urbanization, compelling Civil Engineers to
make the dominantly available soft, Lithomargic Clay (locally known as Shedi Soil), fit for
heavy construction.
Lithomargic Clay is a soft soil, generally classified as silty sand or sandy silt with a high
content of silt. [1] It possess low shear strengths and bearing capacities with high
compressibility. [2] The soil is susceptible to water, losing a significant portion of its strength
under wet conditions. Thus as long as it is confined and dry, there is negligible problem but
when it comes in contact with water, it loses its strength significantly. [3] These factors make
the land highly prone to erosions, slope failures, foundation failures, embankment failures
and uneven settlement over time. The occurrence of such failures has made the development
and application of various ground improvement techniques necessary.
One such widely accepted technique is soil stabilisation. Soil stabilization involves
altering the soil to improve its geotechnical problems, aiming to increase its strength and
softening resistance by bonding the soil particles together or by water proofing the
particles.[4] An economical and efficient method of soil stabilization is using fibres as soil
reinforcements. They are incorporated into the soil either in the form of geogrids or randomly
distributed throughout. Synthetic, for example geomaterials in the form of geogrids,
geotextiles, geofibres, as well as natural fibres, for example coconut coir, jute, etc serve the
purpose. Naturalfibres are desired more from an economical and environmental point of view,
and their use as a soil reinforcement is a big leap towards sustainable building materials.
Coconut coir is one such abundantly available natural, local product. Amongst other
natural fibres, it has the benefit of retaining more than 80% of its tensile strength even after 6
months of its induction into the soil, [5] thus better strength characteristics and resistance to
biodegradation over a longer period. [6]
Apart from these, advances have been made in the field of natural fibre-polymer
composites. These hybrids combine the durability and binding strength of polymers with the
mechanical properties of natural fibres. One such hybrid of coconut coir fibre coated with
Cashew Nut Shell Liquid oil has been proposed in this paper. The oil has been used for
generations as a traditional disinfectant, which can be used to compensate the short life spans
of the natural coir fibres.
1.1. Lithomargic Clay
Lateritic soil is commonly found throughout the entire stretch of the Konkan belt in South
India. This soil is hard and strong, though very porous. 1-3m below the top outcrop of the
soil, Lithomargic clay, an important residual soil of the former, is present. [3] It is whitish,
pinkish, or yellowish in colour with the white particles being the weakest. The soil comprises
of hydrated alumina and kaolinite powder and is a product of tropical and subtropical
weathering. This layer constitutes of particles with size distribution between silt and clay, but
behaves like neither. [7] Under moist conditions, it loses a significant portion of its strength
and tends to flow along with water during heavy rains. This causes the formation of cavities
and uneven settlements on the application of loads, resulting in slope failure. Thus, engineers
have to be very cautious when working with such soil.
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
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1.2. Coconut Coir Fibre
Coir fibre is a hard structural fibre extracted mechanically from the husk of a coconut.
Indigenous to tropical climate, India and other South East Asian countries dominate their
production in the world market. It is abundantly available in the coastal areas of the country,
making it a local, and thus economical, option over other natural fibres. Apart from
contributing to sustainable development, using them as soil reinforcements enhances the
geotechnical nature of the soil. Studies have shown that when they are randomly distributed
in the soil, they maintain a strength isotropy and reduce the possibility of the formation of a
weak zone. It imparts tensile strength to the soil composite which is a key requirement since
the soil under examination possesses high compressive strength but low tensile strength. They
also convert the brittle behaviour of the soil to ductile behaviour due to its ability to undertake
permanent stretch. [6] Compared to other natural fibre, coir fibre has higher lignin content,
making them stronger and more resilient.[8]
1.3. Cashew Nut Shell Liquid Oil
Cashew Nut Shell Liquid Oil (CNSL) is a versatile by-product of the Cashew Industry. It is a
viscous liquid with a honey comb structure, found inside the shell of the nut. It is vastly
produced in the country, with the state of Karnataka producing one third of the total.
It is a renewable and eco-friendly material with a high chemical resistant property. Due to
its anti-microbial and acid resistant properties, it has innumerable applications in the polymer
based industries, along with the energy sector, automobiles, etc. When added to the fibre
reinforcements in the soil, it acts as a disinfectant, improving the durability of the material,
while increasing its strength by providing better bond between the fibre and the soil.
2. LITERATURE REVIEW
The concept of reinforcing soil to increase the shear resistance of the composite was first
introduced by Vidal and since then this field has been subjected to extensive research. Studies
have been conducted to analyse the effect of the aspect ratio and fibre percent of the different
soil properties.
Pradhan, Kumarkar and Naik [9] investigated the effects of aspect ratio and fibre
percentages on the strength parameters of a cohesive soil modified with a synthetic
polypropylene fibre. To avoid the formation of predefined failure planes, the method of
random distribution of fibres was adopted and it was observed that with the initial increase in
the fibre length there was an increase in the shear strength parameters but subsequent
increases resulted in a decreasing trend. This was speculated to be due to the fall in the soil
available for bond formation with the coir fibres. Dasak and Sumesh’s [10] study on the shear
strength of kaolin soil with randomly distributed coir fibres resulted in the same conclusion,
with the optimum fibre length recommended as the lower aspect ratio in the study. Maliakal
and Thiyyakkandi [6] in their study conducted the same tests on the soil to develop a
mathematical model to predict the major principle stress at the failure for the clay-fibre
composite. They conducted experimental studies on two types of clay whose results were
employed to develop the regression model which was then verified with the results of the
third type of clay. Various studied have also been conducted to understand the effects of the
different types of natural fibres available for soil reinforcement. Biswas and Ahsan [11]
studied the various mechanical and physical properties of natural fibres of jute, bamboo and
coconut at different span lengths. On similar lines, Maity, Chattopadhyay and Mukherjee [12]
conducted a comparison of jute, coconut and a locally available Sabai grass on their
effectiveness as reinforcement to natural sand for sub base construction, and the results
showed the better performance of jute and coir over the grass. Ali [5] conducted further
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
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studies on the different chemical and physical properties of coconut coir and their effects as
soil reinforcement. The paper justified the versatility of coir. The results clearly demonstrated
that it was the most tensile of all natural fibres, and its ability to retain it in under different
chemical testing. Apart from the conventional natural fibres used, advances have also been
made in the testing of new locally available materials in soil reinforcement. Adili, Azzam,
Spagnoli and Schrader [13] investigated the effect of papyrus on the strength and stiffness
response of the modified soil, by conducting a series of direct shear tests and consolidation
tests. The paper concluded with the considerable increases observed in the cohesion and
stiffness of the modified soil. Apart from the research work conducted so far, there is still
scope for further development in the field of fibres as soil reinforcement.
3. MATERIALS AND METHODS
3.1. Materials
3.1.1. Lithomargic Clay Soil Sample
The Lithomargic Clay used in the study was obtained from a site near Katpadi-Palli Road,
Udupi District (Karnataka State, India). The soil was encountered at a depth of approx. 1.5-
3m from the surface. Disturbed soil samples, in plastic bags and undisturbed soil samples, in
core cutters were brought to the lab for testing. The properties of the soil obtained after
conducting the basic geotechnical tests have been tabulated in Table 3.1.
Table 3.1 Basic geotechnical properties of the soil sample
Table 3.2 Coir Fibre Properties
Physical property Value
Classification MI
Specific Gravity 2.67
Liquid Limit 49.60%
Plastic Limit 30.39%
Shrinkage Limit 28.36%
Plasticity Index 18.67
Flow Index 15.49
Toughness Index 1.21
Maximum Dry Density 1.548N/mm3
Optimum Moisture Content 25%
Physical property Value
Diameter 0.2mm
Aspect ratio Selected
for the study
75 (l=15mm),
100(l=20mm),125(
l=25mm),150(l=30mm),
175(l=35mm)
Fibre Content Selected
for the Study 0.25%, 0.5%, 0.75%, 1%
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
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a c
b
3.1.2. Coconut Coir Fibres
The coconut coir fibres were attained from Kalpakrutti Karnataka State Coir Development
Corporation near Sastan, Udupi District (Karnataka State, India). The properties of the
coconut coir fibres have been tabulated in Table 3.2.
Figure 1 a. Different layers of soil at site b. Soil Site
c. Undisturbed Soil Sample collected using Core Cutter
a b c
Figure 2 (a) Coconut coir fibre (b). Cashew Nut Shell Liquid Oil (c). Specimen reinforced with
randomly distributed coir fibre for UCS test
3.1.3 Cashew Nut Shell Liquid Oil
The oil used in the study was attained from Anup Industries located in the town of Hiriyedka,
Udupi District (Karnataka State, India). The specifications of the same according to the I.S.
are given in Table 3.3.
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
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3.2. Testing Procedure
To study the variation in the strength characteristics of the soil when reinforced with
randomly distributed untreated coconut coir fibres and coconut coir fibres coated with
Cashew Nut Shell Liquid oil, a series of Unconfined compressive strength tests were
conducted. For this, the aspect ratios, AR (AR=length/diameter) selected were
75,100,125,150 and 175. It was limited to 175 since the corresponding length of fibre was
35mm, which is very close to the diameter of the mould used to conduct the Unconfined
Compressive Strength tests, ensuring placement of the fibres without bending. Fibre
percentage selected were 0.25%, 0.5%, 0.75% and 1% by dry weight of soil.
Table 3.3 IS Specifications of Cashew Nut Shell Liquid Oil
Standard proctor tests were performed on the basis of the guidelines provided in IS:
2720(part VII) 1965, for each combination of AR with the fibre percentages. The UCS and
the DS tests for each combination was conducted with the maximum dry densities and the
optimum moisture content obtained from their corresponding proctor test.
To prepare the specimen for testing, the dry soil was sieved through a 4.25µm IS sieve,
oven dried overnight and then air dried for 30 minutes. The samples were prepared with
utmost care, to ensure uniform mixing of coir and soil to avoid accumulation of the fibres.
For the UCS and the DS tests, dry soil of specified weight was mixed with the required water
content and kept in the dessicator for 15 minutes to attain moisture equilibrium. Coir fibres of
the agreed quantity were then added to the wet soil and again kept in the dessicator for an
hour. This entire process ensured a uniform distribution of the coir fibre with the soil since
fibres tend to segregate when mixed with dry soil.
For the Unconfined compressive tests, the above mix was compacted into a mould of
38mm diameter and 76mm height and tested, according to IS:2720 (Part-X) 1991, till
concurrent results were obtained.
For Direct shear tests, the prepared modified soil was first added to a steel box of the
same dimensions as that of the shear box used (60mm*60mm*35mm),with openings at the
top and the bottom, before being slid into the shear box and tested according to the guidelines
in IS:2720 (Part-XIII) 1972. This practice was adopted due to the sensitivity of the shear box
and to ensure a uniform compaction.
The combination with randomly distributed untreated coir fibres which gave the optimum
results were further tested with a Cashew Nut Shell Liquid (CNSL) Oil coat. The coir was
soaked in the oil, then left to dry under the sun for 48 hours. Once the oil had coagulated, the
same procedure was followed as in the case of untreated coir as reinforcement to conduct the
Physical property Value
Specific Gravity at
30ᵒC 0.95-0.97
Viscosity at 30ᵒC 550
moisture % by weight 1
Loss in weight on
heating 2
Ash % by weight 1
Iodine Value 1
Colour shall not be deeper that dark
brown when viewed by transmitted light
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
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unconfined compressive strength test and direct shear tests. The maximum dry densities and
the optimum moisture contents adopted for the tests were the same as their corresponding
untreated coir reinforcement tests.
3.2.1. Tests on Coconut Coir Fibre
The coconut coir sample used as reinforcement in the study was analysed under a Scanned
Electron Microscope (SEM) to attain the average diameter, and understand its structure and
elemental composition. They were then compared to that of the coconut coir fibre treated
with a coating of Cashew Nut Shell Liquid oil.
4. RESULTS AND DISCUSSSIONS
4.1. Elemental Composition of the Coconut Coir Fibre
The changes in the structural and mineralogical aspects of the untreated coconut coir fibre
when coated with Cashew Nut Shell Liquid oil was studied by analysing them under a SEM.
Images of the sample before and after the application of the oil, magnified to the order of
100X are presented in Fig.3. It can be observed that due to the oil coating, the smooth surface
of the fibre has been converted to a rough, irregular one. This irregularity in the structure will
lead to stronger bond formation, thus increase in the shear strength parameters can be
anticipated.
The elemental compositions of the two coir samples have been tabulated in Table 4.1. It
can be observed that due to the application of the Cashew Nut Shell Liquid oil the Carbon
content and the oxygen content in the fibre has increased and decreased respectively. Traces
of potassium, alumium and silica present in the untreated sample have also vanished in the
treated sample.
a b
Figure 3 Scanned Electron Microscope image of (a) Untreated coir fibre (b) Coir fibre treated with
CSNL Oil
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
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Quantitative results
Weig
ht%
0
20
40
60
80
C O Al Si K
Quantitative results
We
igh
t%
0
20
40
60
80
C O K
a b
Figure. 4 (a) Elemental Composition of Untreated coir fibre Figure 4 (b) Coir fibre treated
with CSNL oil
Table 4.1 Elemental Composition of Untreated coir fibre; Coir fibre treated with CSNL oil
4.2. Randomly Distributed Coconut Coir Fibres as Reinforcement
The strength parameters for the soil reinforced with randomly distributed coir fibres have
been analysed on the basis of the series of Standard proctor tests and Unconfined compressive
strength conducted. Standard proctor tests were conducted to attain the maximum dry density
and the optimum water content for each combination of the proposed aspect ratio and the coir
percentage. Fig 5, Fig6 and Fig.7 presents the density vs. Moisture content for each. It can be
observed that in most of the cases, with the increase in the fibre content, the value of
maximum dry density decreases. This can be attributed to the replacement of the denser soil
with a lighter coir fibre. The field density of the soil was calculated to be 1.308g/cm3, where
as that of coconut coir fibre is on an average 1gm/cm3.
The densities obtained from the above tests were used to conduct compressive strength
tests. The tests were carried out with the MDD and the OMC since they best represent the
field conditions for which the soil requires reinforcement. Fig.8 to Fig.11 present the stress
vs. strain graphs for different aspect ratios. In each graph, the aspect ratio was kept constant
and the effect of the varying fibre percentages was analysed. A general trend of rise in the
compressive strength and then a subsequent fall after reaching the peak can be observed with
Untreated coir fibre
Elements Weight %
C 61.75
O 36.55
Al 0.66
Si 0.62
K 0.42
Coir fibre treated with SNL
Element Weight %
C 76.75
O 22.73
K 0.53
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
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0.0120
0.0130
0.0140
0.0150
0.0160
0.0170
10.00 30.00 50.00
Dry
De
nsi
ty (
N/m
m3)
Water Content (%)
0.75
%
0.50
%
0
0.0120
0.0130
0.0140
0.0150
0.0160
0.0170
10 30 50
Dry
De
nsi
ty (
N/m
m3)
Water Content (%)
Unreinforc
ed
0.25%
0.50%
0.75%
0.0120
0.0130
0.0140
0.0150
0.0160
0.0170
0 50Dry
De
na
ity
(N
/mm
3)
Water Content (%)
Unreinforc
ed0.25%
0.50%
0.75%
1% 0.012
0.013
0.014
0.015
0.016
0.017
5 25 45
Dry
De
nsi
ty (
N/m
m3)
Water Content (%)
Unreinfor
ced
0.25%
0.50%
0.75%
the increase in the percentage of coir fibre added, for all aspect ratios. 0.5% and 0.75% of
fibre to the dry weight of soil showed the maximum increse in strenght, with the value
decreasing again for 1%. Thus, tests were conducted till the addition of only 1% of fibre to
the dry weight of soil. Although the addition of coir fibres are expected to increase the
strength of the soil, the fall can be justified with the decrease in the availability of soil for the
fibre to form an effective bond with. Also, it was observed that this increase in the proportion
of fibre content casuses balling of fibres which leads to the foramation of weak zones. Thus
the maximum percentage added was limited to 1% by dry weight of the soil. Fig11.a presents
the stress vs. Strain curves for the optimum conditions of each aspect ratio. It is clear form the
graph that the highest increase was witnessed for the aspect ratio 75 with a 0.5% fibre
content. The compressive strength increased by 92% from the unreinforced soil.
Thus the unconfined compressive tests concluded that soil reinforced with randomly
distributed coir fibre of aspect ratio 75 with a 0.5% fibre content provided the optimum
results.
a b
Figure 5. Dry Density vs. Water content curves for Soil reinforced with untreated coir fibre randomly
distributed at (a) AR =75 (b) AR=100
A b
Figure 6 Dry Density vs. water content curves for Soil reinforced with untreated coir fibrerandomly
distributed at (a) AR =125 (b) AR=150
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
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0
0.05
0.1
0.15
0.2
0.25
0.3
0.000 5.000
Str
ess
(N
/mm
2)
Strain%
Unreiforced
SoilAR 100 (0.25%)
AR 100(0.5%)
AR 100 (0.75%)
AR 100 (1%)
0
0.1
0.2
0.3
0.4
0.0 2.0 4.0 6.0
Str
ess
(N
/mm
2)
Sttrain %
Unreinforced
AR75 (0.25%)
AR 75 (0.5%)
AR75(0.75%)
AR 75(1%)
0.012
0.013
0.014
0.015
0.016
0.017
5 25 45
Dry
De
nsi
ty (
N/m
m3)
Water Content %
Unrein
forced0.25
0.5
0.75
1%
Figure 7 Dry Density vs. water content curves for Soil reinforced with untreated coir fibre randomly
distributed at AR=175
Figure 8 Stress vs. Strain curves for Soil reinforced with untreated coir fibre randomly distributed at
(a) AR =75
a b
Figure 9 Stress vs. Strain curves for Soil reinforced with untreated coir fibre randomly distributed at
(a) AR =100 and (b) AR=125
0
0.05
0.1
0.15
0.2
0.25
0.3
0.0 5.0
Str
ess
(N
/mm
2)
Strain %
Unreiforced
Soil
AR
125(0.25%)
AR 125
(0.5%)
AR 125
(0.75%)
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
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0
0.1
0.2
0.3
0.000 5.000 10.000
Str
ess
(N
/mm
2)
Strain %
Unreiforced
Soil
AR 150
(0.25%)
AR 150
(0.5%)
AR 150
(0.75%)
0
0.1
0.2
0.3
0.000 2.000 4.000
Str
ess
(N
/mm
2)
Strain%
Unreiforced
Soil
AR
175(0.25%)
AR 175
(0.5%)
AR
175(0.75%)
(a) (b)
Figure 10 Stress vs. Strain curves for Soil reinforced with untreated coir fibre randomly distributed at
(a) AR =150 and (b) AR=175
Figure 11. (a)Stress vs. Strain curves for Soil reinforced with untreated coir fibrerandomly distributed
at the optimumfibre percentage for each Aspect Ratio.(UCS Test)
Figure 12 UCS Test specimen for soil reinforced with randomly distributed untreated coir fibre
0
0.050.1
0.150.2
0.250.3
0.350.4
0.000 5.000
Str
ess
(N/m
m2)
Strain %
Unreiforced Soil
AR 75 (0.5%)
AR 100 (0.5%)
AR 150 (0.75%)
AR 125 (0.75%)
AR 175 (0.5%)
Strength Characteristics of Randomly Distributed Coconut Coir Reinforced Lithomargic Clay
http://www.iaeme.com/IJCIET/index.asp 1133 [email protected]
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 2 4 6 8
Str
ess
(N/m
m2
)
Strain %
Unreinfiorced soil
Soil reinforced
with randomly
distributed
untreated coir
fibre
Soil reinforced
with randomly
distributed coir
fibre coated with
CSNL Oil
4.3. Randomly Distributed Coconut Coir Fibres Coated with Cashew Nut Shell
Liquid Oil as Reinforcement
The study on the soil reinforced with randomly distributed coconut coir fibres concluded with
the maximum strength characteristics observed at aspect ratio of 75 were added in 0.5% of
the dry weight of the soil. This combination was further examined by coating the coir fibres
in CSNL oil. The compressive strength increased by 4.41% from when untreated coir fibres
were used as reinforcement and by 100% from the unreinforced soil. The peak value was
attained at a higher strain percent, indicating an increase in the ductility of the sample.The
increase in strength when CNSL oil is used can be attributed to its binding characteristic. As
indicated by the images produced by analysing the sample under SEM, the oil causes a
development of an irregular coat on the fibre; this improves the adhesion between the treated
coir fibres with the soil which improves the cohesion of the modified soil.
Figure 13 Stress vs. Strain curve for soil soil reinforced with randomly distributed coir fibre coated
with CSNL Oil (UCS Test)
5. CONCLUSION
The study was undertaken to understand the nature of the locally available Lithomargic Clay
and propose soil modification techniques to improve its strength. The proposed soil
modifications were reinforcing the soil with randomly distributing untreated coconut coir
fibres and then by adding a coat of Cashew Nut Shell Liquid Oil on the fibres. The following
conclusions were drawn,
• With the use of coconut coir as reinforcement, a significant increase in the
strength characteristics of the soil was witnessed.
• As the aspect ratio and the fibre percent increased, a fall in the maximum dry
density was observed due to the replacement of soil with coir fibres of lower
specific gravity.
• For unconfined compressive strength of the modified soil, after an initial rise in
the value with the increase in the fibre percent for a particular aspect ratio, a fall in
the strength was observed. This can be attributed to the decrease in the quantity of
soil available for bond formation with the coir fibres.
Purushotham G. Sarvade, Deepak Nayak, Aayush Sharma, RaginiGogoi and SagarMadhukar
http://www.iaeme.com/IJCIET/index.asp 1134 [email protected]
• With untreated randomly distributed coir fibres as reinforcement, optimum
strength characteristics were obtained for an aspect ratio of 75 with 0.5% fibre at
dry weight of soil for unconfined compressive strength test .
• A further improvement in the strength parameters along with the ductility of the
modified soil was observed when the coconut coir fibres were coated with Cashew
Nut Shell Liquid oil.
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