2. Abstract
The main objective of this study is to investigate the use of
waste fiber materials in geotechnical
applications and to evaluate the effects of waste polypropylene
fibers on shear strength of unsaturated
soil by carrying out direct shear tests and unconfined
compression tests on two different soil samples. The
results obtained are compared for the two samples and
inferences are drawn towards the usability and
effectiveness of fiber reinforcement as a replacement for deep
foundation or raft foundation, as a cost
effective approach
3. Content:-
Introduction
Objectives
Types of stabilizers
Why plastic ?
Properties of plastic
Advantages of plastic
Literature reviews
Materials and methodology
Results
Conclusion
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4. Introduction:-
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•Soil stabilization is the process of improving the engineering properties of the soil and
thus making it more stable . In its broadest senses, stabilization include compaction ,
preconsolidation, drainage and many other processes.
•Soil stabilization is used to reduce to the permeability and compressibility of the soil
mass in earth structure and to increase its shear strength. However , the main use of
stabilization is to improve the natural soil for the construction of highways and make an
area trafficable with in a short period of time for military and other emergency purposes.
•In India , the modern era of soil stabilization began in early 1970’s, with a general
shortage of petroleum and aggregates, it became necessary for the engineers to look at
means to improve soil other than replacing the poor soil at the building sites.
5. Objectives of soil stabilization:-
Increased shear strength
Reducing permeability and shrinkage cracks
California Bearing Ratio (CBR) of the soil
It can significantly enhance the properties of the soil used in the construction of road
infrastructure.
Soil stabilization is to improve on site material to create a solid and strong sub-base and base
courses.
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6. Types of Stabilization :-
Mechanical or granular stabilization
Cement stabilization
Lime stabilization
Bituminous stabilization
Chemical stabilization (calcium chloride, sodium chloride, sodium silicate or water glass)
Electrical stabilization or electro osmosis(mainly used for drainage of cohesive soils)
Stabilization using grouting
Stabilization by geotextile and fabrics
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7. Selection of topic(plastic as a soil stabilizer):-
The use of plastic fibers soil tremendously increases CBR value, shear strength,
resistance to cracking , reduces consolidation and swelling properties in soil.
Disposal of these different waste produced from different industries and urban areas
become a great problem .the estimated municipal solid waste are production in India up
to the year 2000 was of order of 50 million tones per year.
Performance of the paved and unpaved roads are often poor after every monsoon and in
most pavements are seen cracking, potholes , wheel path rutting and serious differential
settlement at various locations so these must we effectively reduces by using plastic as a
soil stabilizer(as reinforcement for soil).
8. Properties of soil can be improved by using
waste plastic as stabilizer:-
CBR value
Increase shear strength
Reduction in consolidation settlement
Reduction in swelling
Reduction in cracks
Avoids disposal problems of plastics
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9. Major function performed by introducing
waste plastic:-
Plastic as separators:-plastic are commonly used as separators between two layers of
soils having large difference in particle sizes to prevent migration to small sizes particle
in to the voids of large sizes particle. The main use as separators is in the construction
of highways on clay soils. thus a plastic sheet is used between the sub-grade and the
base course.
Plastic as reinforcement for strengthening soil:- plastic are used as reinforcement
in the soil , which is poor in tension but good in compression(soft soil). The action is
somewhat similar to that of steel bars in a reinforced concrete slab.
10. Plastic as filter:- To provide a properly graded filter to prevent the movement of soil
particles due to seepage forces. When the silt laden turbid water passes through the
plastic, the silt particle are prevented from movement by geotextile and migration of the
particle of the core in to the shells.
Plastic as drain:- A drain is used to convey water safely from one place to the other.
As the plastic are pervious , they themselves function as drain. they have a relatively
higher water carrying capacity as compared to that of the surrounding soil.
11. Advantages of soil stabilization:-
•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.
•Sometimes soil stabilization is also used to prevent soil erosion or formation of dust, which is very
useful especially in dry and arid weather .
•Stabilization is also done for soil water proofing for , this prevents water from entering in to the soil
and hence helps the soil from losing its strength.
•It helps in reducing the volume change due to change in moisture content and temperature.
12. Literature review:-
(following review of literature relevant to the present topic of research are given below)
Waldron(1977) :-carried out direct shear test using a large direct shear device to study the effect
of plant roots on the soil shearing resistance.
Gray and ohashi(1983):- conducted a series of direct shear test on dry sand reinforced with
synthetic (PVC) and metallic (copper wire) fibers to evaluate the effect of shear strength based on
experimental results.
Setty and rao (1987):-carried out a triaxial test, CBR tests and tensile strength tests on silty
sands, reinforced with randomly distributed polyprolene fibers.
Lindh and Eriksson (1990):-conducted field experiments to study the suitability of fibers for
road construction. The effect of the plastic fibers on the stability of the sand was observed be
good.
Ranjan et al.(1996):-conducted a series of triaxial compression tests on soils reinforced with
discrete, randomly distributed fibers both synthetic (plastic) and natural (coconut coir).
13. Materials and experimental work:-
Material:-
Soil sample:-
Location:- Sumel, Near Kanota, Jaipur
Plastic sample:-
Location:- Near Disposal Sites Beelwa
14. Experimental work:-
a brief description of the methods used in this investigation are as follows-
(a) Specific Gravity of soil:-
The specific gravity of soil is defined as the ratio between the weight of the soil solid
and weight of equal volume of water.
The specific gravity test is done by following procedure.
(1) A sample of oven dry soil, about 300g is taken in the pycnometer and take
weighted W2.
(2) After that the pycnometer is filled with water and entrapped air removes by using a
glass rod W3
(3) The pycnometer is wiped dry and take weighting WI .
(4) The pycnometer is filled with water (only water) and take weighted W4.
(5) By the following formula G= ( W2- W 1 )/{W2 –W1) –(W3-W4)}
Figure:-Pycnometer
15. (b) Particle Size Distribution:-
Sedimentation analysis for fine grained soil (clay):-soil particles finer than 75µ size cannot be
sieved. The particle size distribution of such soils is determined by sedimentation analysis. The
analysis is based on Stokes’s law, which settles in a fluid, its velocity first increase under the action of
gravity , but the drag force comes into action, and retards the velocity. After an initial adjustment
period, steady conditions are attained and the velocity becomes constant. The velocity attained is
known as terminal velocity. The expression for terminal velocity can be obtained from the
equilibrium of the particle.
where,
D = Diameter of the sphere in cm.
ƞ = Viscosity in poise
He = Spherical falls through a height He in cm in t sec.
pw = water density in gm/ml
g = acceleration due to gravity in cm/sec2
sand 2.63 to 2.65
silt 2.67 to 2.7
Clay and silty clay 2.67 to 2.9
Organic clay <2.0
specific gravity standard values for soil
16. (c) Atterbergs Limits
.
1. Shrinkage Limit
This limit is achieved when further reduction in water content does not change the volume of the
soil. It can be more accurately defined as the lowest water content at which the soil can be still
completely saturated. It is denoted by Ws.
2. Plastic Limit
This limit exists between the plastic and semi -solid state of the soil this is determined by rolling out
t thread of the soil on a non -porous flat surface. The minimum water content at which the soil just
begins to crumble while rolling into a thread of 3mm diameter is termed as plastic limit. It is
denoted by Wp.
The Plastic limit test is done by following procedure.
a) Soil specimen passing 425µ IS -Sieve is mixed thoroughly with the distilled water until the soil
mass because plastic enough to be moulded with the fingers.
17. b) A ball is formed with about 10gm of this plastic soil and rolled between the
fingers and a glass plate with just sufficient pressure to roll the 'Toss in to thread of
uniform diameter throughout its length.
c) When by such rolling the thread starts just crumbling at a diameter of 3mm. The
sample is at its plastic limit these crumbled threads are kept for water content
determination.
d) The test is repeated twice more with the fresh soil sample and plastic limit is then
taker as the average of the water contents.
Ip =Wl - Wp
Wl - Liquid Limit
Wp-Plastic Limit
18. 3. Liquid Limit
It is the water content of the soils between the liquid state and plastic state of the soil. It
can be defined as the minimum water content at which the soil, though in liquid state,
shows small shearing strength against flowing. It is measured by the Casagrande's
apparatus and is denoted by W1.
The liquid limit test is done by following procedure.
a) We took about 120 grams air dried soil sample passing 425µ sieves.
b) The sample was placed in tray and sufficient quantity of water is added to make it
paste.
c) A portion of this soil is placed into the apparatus cup and level to a depth 1 cm.
d) The sample was divided by means of grooving tools long the diameter of cup.
e) The crane was related uniformly till the bottom of grove closed to a distance of
13mm.
f) The numbers of blows were counted which were imparted to the brass cup.
g) Some of the paste was placed in crucible for determination of water content into
different moisture content.
Figure :- casagrande’s apparatus
19. d) Proctor Compaction Test
This experiment gives a relationship between the dry density of the soil
and the moisture content of the soil. The experimental setup consists of
(i)cylindrical metal mould (internal diameter- 10 cm and internal height-
12.75 cm),
(ii) Detachable base plate,
(iii) Collar (5 cm effective height)
(iv) Rammer (2.5 kg). Compaction process help in increasing the bulk
density by expulsion of air from the voids. The maximum dry density
(MDD) is achieved when the soil is compacted at relatively high
moisture content and almost all the air is expelled out, this moisture
content is called optimun1 moisture content (OMC).
20. Range of optimum water content
sand Sandy silt
or silty
sand
silt clay
6 to 10% 8 to 12% 12 to 16% 14 to 20%
Figure:- standard proctor test
21. e) CBR Test
California bearing ratio (CBR) is determined of a compacted soil sample in the laboratory in
soaked state.
The CBR test is done following procedure.
a) Firstly find out the OMC and MDD of the soil sample and mix with the soil sample and make a
paste.
b) Compact the mixed soil in the mould using either the light compaction or heavy compaction.
c) Put filter paper on the top soil (collar side) and clamp the perforated of the compacted base plate
on to it.
d) Place the surcharge 'eights hack on the top of the soaked soil. Specimen, and place mould
assembly on the penetration test machine (loading machine)
e) Seat the penetration piston at the center of the specimen with the smallest possible load but in no
case excess of 4kg so that l contact is established between the surface of the specimen and the
piston.
f) Set the stress and strain dial gauge to zero. Apply the load on the penetration piston so that
penetration rate is approximately 1.25 mm/min. record the load reading at penetration of Record
the maximum 0,0.5,1.0,1.5,2.0,2.5,3.0,4.0,5.0,7.5,10 and 12.5 mm. load and penetration if it occurs
for a penetration of less than 12.5 mm.
g) At the end of the penetration test detach the mould from the loading equipment. Take about 20 to
50 g soil from the top 3 cm layer of the specimen and keep it for water content determination.
h) Draw the graph between the %age CBR and Dry Density, and find CBR at required degree of
compaction.
.
22. Uses and Significance of California Bearing Ratio Test:
The CBR test is one of the most commonly used methods to evaluate the
strength of a sub grade soil, sub base, and base course material for design of
thickness for highways and the air field Pavement.
The California bearing ratio test is penetration test meant for the evaluation of
sub-grade strength of roads and pavements. The results obtained by these
tests are used with the Empirical curves to determine the thickness of
pavement and its component layers. This is the most widely used method for
the design of flexible pavement. instruction sheet covers the laboratory
method for the determination of CBR of undisturbed and remolded
compacted soil specimens, both in soaked as well as un-soaked state
23. Results of Experimental Work:-
Material property results
Soil Engineering Property value
Natural water content 10.7%
Specific gravity of soil 2.78(silty clay)
Liquid limit 34%
Plastic limit 22.5%
MDD(maximum dry density in g/cc) 1.74
OMC(optimum moisture content) 16.66%(clay)
CBR(california bearing ratio) of natural soil
At 2.5 mm penetration
At 5 mm penetration
2.87
2.71
Optimum value of CBR after introducing of
1.5% plastic
(a) At 2.5 mm penetration
(b) At 5 mm penetration
5.98
5.58
24. Various properties of the optimum mix of plastic and soil
Soil Engineering property value
MDD(maximum dry density in
g/cc)
1.71
OMC(optimum moisture
content)
17.64%
CBR(california bearing ratio) 5.98
25. Conclusion:-
Based on the work an experimental study following conclusion are made
• As the percentage of plastic was increased in the mix, MDD values have shown a
continuous decline up to adding 1% plastic then increased at 1.5% plastic add then
again decreased.
• On the other hand OMC values were kept increasing upon increasing percentage of
plastic. This means as the amount of plastic increases it takes more amount of water
content for the mixture to each its maximum dry density.
• CBR values have shown a mixed nature. These values were increasing up to 1.5%
inclusion of plastic in the mix and thereafter decreasing if percentage of plastic is
increased further.
• Hence it can be said that use of plastic in subgrade can enhance its stability up to a
certain quantity. After that optimum content further addition of plastic in the subgrade
has detrimental effects on the stability.
• According to the study made with the collected samples of plastic and soil, optimum
mix was found to be mixture of soil and 1.5% plastic owing highest value of CBR of
5.98 in comparison to soil CBR of 2.87%.
• It should be noted that properties of soil as well as plastic depends largely upon their
source. So composition of optimum mix can change depending upon the origin.
