PLASTIC AS A SOIL STABILZER (A.S. Aswathy, Greeshma.V.R, Arunachala College of Engineering for Women) ABSTRACT
INTRODUCTION
Soil stabilization is the permanent
Soil stabilization can be done in
physical and chemical alteration of soils to
many
enhance
properties.
using waste plastic fibers is an economic
Stabilization can increase the shear strength
method since the stabilizer used here
of a soil and control the shrink-swell
is waste plastic materials, which are easily
properties of a soil, thus improving the load-
available. A plastic material is any of a wide
bearing capacity of a sub-grade to support
range of synthetic or semi-synthetic organic
pavements and foundations. Stabilization
solids
can be used to treat a wide range of sub-
typically organic plastics of high molecular
grade materials from expansive clays to
mass,
granular materials. Stabilization can be
substances. They are usually synthetic, most
achieved
commonly derived from petrochemicals, but
their
with
physical
a
variety
of
chemical
additives including lime, fly ash, and
ways.
that
but
But
are
the
moldable.
they
often
stabilization
Plastics
contain
are
other
many are partially natural.
Portland cement, as well as by-products such as lime-kiln dust and cement-kiln dust. These are the existing techniques to improve
PLASTIC AS A SOIL STABILIZER
soil stabilization. This paper presents the
In the investigation the waste
details of studies conducted on the possible
plastic materials has been chosen as the
use of waste plastic for soil stabilization. We
reinforcement material and it was randomly
think that the addition of plastic strips into
included in to the clayey soils with different
the soil will be a innovative technique to
plasticity
improve
strength, tensile
percentages of fiber content (0%, 1%,2%,
strength and California bearing ratio (CBR)
3%, 4%) by weight of raw soil. The use of
value of the soil in an economic way.
plastic
the
shear
indexes
fibers
in
at
five
different
unreinforced
soil
tremendously increases the CBR value, Shear Strength, Resistance to desiccation
cracking,
reduces
Consolidation
and
Swelling.
was performed on them. The samples examined for this purpose were prepared by
IMPROVED PROPERTIES OF SOIL BY USING PLASTIC AS SOIL STABILISER
adding 5, 15 and 25% cement and 0.1, 0.15, 0.2 and 0.5% polypropylene fibers. The sample which showed the maximum value of CBR after 90 days of curing was chosen
i)
CBR Value
as the optimum percentage of polypropylene
ii)
Increased shear strength
fibers for further evaluation of strength of
iii)
Reduction
the stabilized peat soil.
in
consolidation
settlement iv)
Reduction in swelling
v)
Reduction in cracks
vi)
Avoids
disposal
Effect of stabilization on CBR value
The problems
of
plastic
results
of
CBR
tests
for
stabilized peat soil samples with cement and polypropylene fibers after air curing for 90 days .The CBR value of undisturbed peat
i)
soil is 0.785%. With the addition of 50%
CBR VALUE
The
California
bearing
ratio
(CBR) is a penetration test for evaluation of the mechanical strength of soil. To find out the change of CBR value of the fiber reinforced soil with respect to unreinforced soil, CBR test is conducted.
cement, it increased to 34% for unsoaked condition and 30% for the soaked condition. With the addition of 0.15% polypropylene fibers with 50% cement, this increased to 38% and 35% for unsoaked and soaked conditions. The results indicate that as cement amount in the mixture is increased,
In this study, in order to find the
the CBR values also increase and addition of
optimum percentage of fiber content for the
polypropylene
stabilized peat soil that would provide the
increase of the CBR values.
maximum strength, peat soil samples at their natural water content were mixed with different
percentages
of
cement
fibers
causes
a
further
INCREASED SHEAR STRENGTH
and
This experimental work has
polypropylene fibers and were cured in air
been performed to investigate the influence
for a period of 90 days and then CBR test
of Plasticity Index and percentage of waste
plastic materials on the shear strength of
due to the addition of the waste plastic fibers
waste plastic materials on the shear strength
and it is a non linear function. Up to a
of unsaturated clayey soils. For this purpose,
critical fiber content shear strength increased
clayey soils with different plasticity Indexes
considerably and later small reduction is
were
observed. However shear values are greater
used
and
mixed
with
different
percentage of waste materials to investigate the
shear
strength
parameters
of
unreinforced and reinforced samples in terms
of
direct
shear
than unreinforced soil. ii)
REDUCTION
IN
CONSOLIDATION
test.
SETTLEMENT
In order to determine the shear strength parameters parameters (C and φ) of unreinforced unreinforced and
In order to assess the effect of
reinforced samples, a series of shear box
random fiber inclusion on consolidation
tests at vertical normal stresses of 100-300
settlement,
KPa and strain rate of 0.2% mm/min were
conductivity,
carried out in accordance with ASTMD
conducted according to ASTM D2435-96. In
3080.shear stresses were recorded as a
the current investigation all samples were
function of horizontal displacement up to
prepared using the same dry density and
total displacement of 17 mm to observe the
molding moisture content equal to 70% of
post failure behavior as well. Verification
the liquid limit.
tests were also performed in order to examine
the
repeatability
of
swelling oedometer
and
hydraulic tests
were
Consolidation settlements results
the Effects of random fiber inclusion on
experiments. Effects of stabilization on shear strength
consolidation settlement of soil samples were evaluated as function of fiber length,
Soil because
can
the
be
non-liner
variation
reinforcement
materials
exhibited a distribution with
In general
angle of internal friction increased with fiber content. The variation of with percentages of fiber contents leads to a conclusion that the behavior of the fiber included. The shear strength of fiber reinforced soil is improved
content and consolidation pressure. Prior to the fiber inclusion, consolidation settlement of unreinforced soil sample was determined. A Constant pressure, increasing the fiber contents from 1 to 8% resulted in reducing consolidation settlement of the samples. This is a common trend with all fiber lengths
examined.
Maximum
and
minimum
fibers having 5mm length which is a
consolidation settlements of 7.5 and 2.6 mm
substantial
were
the
constant fiber contents, an increase in the
sample
fiber length from 5 to 10mm resulted in a
reinforced by 8% fibers having 5mm length .
slight increase in swelling. As a whole,
This shows a reduction in consolidation
however, the increase in the fiber length did
settlement of approximately 25%.
not have a significant effect on swelling
respectively
unreinforced
measured
sample
REDUCTION
and
IN
for
the
SWELLING
Oedometer was used for swelling saturated on molding; they showed no affinity for further water absorption after flooding
the
oedometer
water
bath.
Therefore, they did not exhibit much free swelling in order to be able to assess the effects
of
fiber
inclusions
on
this
characteristic. Therefore, volume changes during
the
unloading
stage
of
the
consolidation tests were measured and used as an indication of the possible effects of
maximum consolidation pressure of 200kPa.
in
swelling.
For
reduction. This was particularly true when the fiber contents remained constant. It can therefore be concluded that with the increase in fiber contents and lengths, the soil/fiber surface interactions were increased. This resulted in a matrix that binds soil particles and
effectively
resists
tensile
stresses
produced due t swelling. Resistance to swelling is mainly attributed to cohesion at the
soil/fiber
interfaces.
DESICCATION
fiber inclusion on swellings. The swellings presented were measured after unloading the
reduction
CRACKS
Oedometer
rings
were
used
to
investigate the effects of random fiber inclusion on desiccation cracking of the soil. After molding, confining rings containing
Effects of swelling test
the specimen were placed in open air in the
It can be seen that by increasing the fiber content, the amount of swellings decreased.
The
unreinforced
sample
produced the highest swelling of about 3.4mm. This was reduced to approximately 1.5mm for the sample reinforced with 8%
laboratory at a temperature of about 30°C. Samples were regularly weighed and when no
changes
in
three
consecutive
measurements were observed, they were considered completely dried. Then, samples were used for observational examination of
the
extent
of
cracking.
solution to waste treatment with the advent of soil reinforcement.
Effects
of
desiccation
Observational
cracks
examination
of
samples after desiccation showed that by increasing the fiber contents and lengths, the extent and depth of cracks were significantly reduced. It can be seen that extensive, deep and wide cracks were formed in the unreinforced sample. The reinforced sample, however, has mainly experienced separation from the metal ring with no visible sign of cracks forming within the sample. This clearly shows the effectiveness of random fiber inclusion in resisting and reducing desiccation cracking which is of paramount importance in surface cracking of clay covers used in landfills. Therefore, it can be concluded that random fiber inclusion seems to be a practical and effective method of increasing tensile strength of the clayey soils to
resist
volumetric
changes.
CONCLUSION
Plastic is one of the major toxic pollutants of our time. Being a nonbiodegradable substance, composed of toxic chemicals, plastic pollutes earth, air and water. Beside all these ill il l effects we here suggested one method which drastically change the view by which the people are concerned it today. Here without affecting the normal texture of the soil we are stabilizing it with the fiber format of the plastic. REFERENCES
1. Carol J. Miller and Sami Rifai, (2004), “Fiber
Reinforcement
Containment
Soil
for
Waste
Liners”,
(ASCE)
Journal,(1-5).
2. S. A. Naeini and S. M. Sadjadi ,(2008) ,” Effect of Waste Plastic Materials on Shear
Strength of Unsaturated Clays”, EJGE REDUCE
ENVIRONMENTAL
HAZARDS
The most important point is the environmental concern regarding the effects of waste plastic in soil and the problems and threats that is related with their excessive usage and disposal. This gives an effective
Journal,
Vol
13,
Bund
k,(1-12).
