11-01-2014, 04:11 PM
A STUDY ON CBR BEHAVIOR OF WASTE PLASTIC STRIP REINFORCED SOIL
STUDY ON CBR BEHAVIOR.pdf (Size: 131.6 KB / Downloads: 61)
ABSTRACT
The performance of paved and unpaved roads is often poor after every monsoon and, in most
cases; these pavements show cracking, potholes, wheel path rutting and serious differential
settlement at various locations. Therefore, it is of utmost importance considering the design and
construction methodology to maintain and improve the performance of such pavements. Attempts
have been made in the study to demonstrate the potential of reclaimed high density polyethylene
strips (HDPE) as soil reinforcement for improving engineering performance of subgrade soil.
HDPE strips obtained from waste plastic were mixed randomly with the soil. A series of
California Bearing Ratio (CBR) tests were carried out on randomly reinforced soil by varying
percentage of HDPE strips with different lengths and proportions. Results of CBR tests
demonstrated that inclusion of waste HDPE strips in soil with appropriate amounts improved
strength and deformation behavior of subgrade soils substantially. The proposed technique can be
used to advantage in embankment/road construction.
INTRODUCTION
Nowadays, plastic containers usually made of high
density polyethylene (HDPE) are being increasingly
used for storage and marketing of various liquids.
Most of these containers are specifically made for spot
use, having short life span and are being discarded
immediately after use. Though, at many places HDPE
is being collected for recycling or reuse, however; the
secondary markets for reclaimed HDPE have not
developed as recycling program[1]. Therefore, the
quantity of HDPE that is being currently reused or
recycled is only a fraction of the total volume
produced every year[2]. According to the data
published by Environmental Protection Agency (US
Environmental Agency 1992), the solid waste
produced in the US in 1988 included 14.4 million tons
of plastic occupying 20% by volume of available
landfill spaces. Approximately 2.2 million tons of
HDPE are produced annually and only 7% are
currently being recycled. The estimated municipal
solid waste production in India up to the year 2000
was of the order of 39 million tons per year. This
figure is most likely to touch 56 million tons per year
by the end of 2010[3].
BACKGROUND
Soil fiber composites have been found effective in
improving the CBR value as reported in the
literature[10-14]. These studies indicated that stress-
strain-strength properties of randomly distributed fiber
reinforced soil are a function of fiber content and
aspect ratio. Considerable improvement in frictional
resistance of fine grained soil was also reported by
roughened HDPE[15]. In addition, use of polyethylene
fiber (plastic waste) improved peak and ultimate
strength of both cemented and un-cemented soil[16].
Strength and load bearing capacity of soil was
enhanced considerably when the soil is stabilized
mechanically with short thin plastic strips of different
length and content[4, 7]. The feasibility of reinforcing
soil with strips of reclaimed high density polyethylene
has also been investigated to a limited extent[17-19]. It
has been also reported that the presence of a small
fraction of HDPE fiber can increase the fracture
energy of the soil. Although, a few studies on the
subject of engineering behavior of HDPE reinforced
soil as described earlier are available in literature but a
detailed study pertaining to its use in real life problems
is still quite meager. In view of the above limited
studies, present study has been taken up with special
reference to its feasibility for application in
embankment/road construction.
CONCLUSIONS
The feasibility of reinforcing soil with strips of
reclaimed HDPE was investigated in this study. Strips
of HDPE were mixed with local sand and tested to
determine CBR values and secant modulus. The tests
show that reinforcing sand with waste HDPE strips
enhances its resistance to deformation and its strength.
Based on the results, the following conclusions can be
drawn:
1. The addition of reclaimed HDPE strips, a waste 9.
material, to local sand increases the CBR value and
secant modulus.
2. The maximum improvement in CBR and secant 10.
modulus is obtained when the strip content is
4% and the aspect ratio 3.
3. The reinforcement benefit increases with an
increase in waste plastic strip content and length.
4. The maximum CBR value of a reinforced system is
approximately 3 times that of a unreinforced
system.