3223
Utilisation of polyethylene (plastic) shopping bags waste for soil improvement in
sandy soils
Utilisation des déchets de sacs en polyéthylène (plastiques) pour l'amélioration des sols sableux
Kalumba D., Chebet F.C.
University of Cape Town, South Africa
ABSTRACT: This study investigated the possibility of utilising polytheylene shopping bags waste to reinforce soils to pave way for
its use in civil engineering projects such as in road bases, embankments and slope stabilisation. A series of direct shear tests was
undertaken on soil-plastic composites of two selected sandy soils: Klipheuwel and Cape Flats sands. Strips of shredded plastic
material were used as reinforcement inclusions at concentrations of up to 0.3% by weight. The effect of varying dimensions of the
strips was investigated by using strip lengths from 15 mm to 45 mm and strip widths from 6 mm to 18 mm. Shear strength parameters
were obtained for composite specimen from which analyses were done to identify the extent of soil improvement. The testing
programme involved addition of solid strips as well as perforated strips with varied diameter of perforations to examine the effect of
the openings on the strips. Laboratory results obtained favourably suggest that inclusion of this material in sandy soils would be
effective for ground improvement in geotechnical engineering.
RÉSUMÉ : Cette étude a examiné la possibilité de l’utilisation des déchets des sacs d’épicerie en polyéthylène pour renforcer les sols
afin de promouvoir son intégration dans les projets de génie civil tels que les couches d’assise des routes, les remblais et la stabilité
des pentes. Une série d’essais de cisaillement direct a été réalisée sur des composites plastique-sols sur deux sols sableux sélectionnés
: sable de Klipheuwel et de Cape Flats. Des lamelles de matériau plastique déchiqueté ont été utilisées comme intrants de
renforcement à des concentrations allant jusqu’à 0,3% du poids. L’effet de la variation des dimensions des lamelles a été apprécié en
modifiant leurs longueurs de 15 à 45 mm et leurs largeurs de 6 à 18 mm. Les paramètres de la résistance au cisaillement obtenus pour
les spécimens de composites ont servi à faire des analyses pour l’estimation du degré d’amélioration des sols. Le procédé scientifique
a été fait avec des lamelles pleines et des lamelles perforées à divers diamètres afin d’observer l’effet des interstices dans les lamelles
perforées. Les résultats de laboratoire obtenus confirment favorablement que l’ajout de ce matériau dans les sols sableux serait
efficace pour l’amélioration des sols dans les applications d’ingénierie géotechnique.
KEYWORDS: Plastic bags, Polyethylene, Waste minimisation, Soil reinforcement, Ground improvement, Shear strength
1 INTRODUCTION
Increased use of plastics in day to day consumer applications
has resulted in municipal solid waste containing an ever
growing fraction of plastic material used for a short time and
discarded. Ever since their invention over 60 years ago, plastics
have taken centre stage in daily life due to favourable attributes
such as low weight, durability and lower cost as compared to
other material types (Thompson et al. 2009, Andrady and Neal
2009). These attributes make plastics convenient and therefore
highly demanded by consumers with production increasing
substantially from about 0.5 million tonnes in 1950 to over 260
million tonnes by 2008 with higher projections expected in the
future (Thompson et al. 2009). A large percentage of plastics
produced are used for disposable applications like packaging
and therefore reach the waste stream more quickly since their
usage life is shorter than that of plastics used in the construction
or automotive industry (Azapagic et al. 2003). Consequently
about 10% by weight and 20% by volume of the municipal
waste stream is composed of plastics destined for landfills
(Barnes et al. 2009, Azapagic et al., 2003). Of the plastic
material discarded, 50% is from packaging, a third of which
consists of plastic shopping bags (Nhamo 2008).
Plastic shopping bags are water resistant materials mostly
made of polyethylene, a non-biodegradable polymer produced
from non-renewable petroleum and natural gas resources. The
linear consumption patterns of plastic bags involving single
usage and then disposal has led to environmental challenges
such as diminishing landfill space, marine and urban littering.
There is therefore a growing need to find alternative uses of
reclaimed plastic bag waste to lengthen the usage time of the
plastic material. This is so as to tap into the abundant plastic
resource that possesses a great extent of versatility and yet in
the same vein poses a danger to the environment if not well
managed in terms of responsible disposal that involves resource
recovery vital in contributing to sustainable development.
Chen et al. (2011) maintain that new approaches on the reuse
of plastic waste in cities as alternative materials for urban
developmental programs, referred to as urban symbiosis, could
help reduce green house gas emissions and fossil fuel
consumption. This study explored the possibility of utilising
reclaimed plastic material from polyethylene bags as tensile
inclusions to reinforce soil for ground improvement schemes in
geotechnical engineering applications such as retaining walls,
road bases, embankments and slope stabilisation.
Research into random inclusion of discrete polypropylene
fibres in soil as reinforcement material have reported increases
in peak shear strengths and reductions of post peak losses in
soils (Zornberg 2002, Consoli
et al
., 2007, Falorca and Pinto
2011). Furthermore, these fibres have been found to improve
compressive strength and ductility of soils (Maher and Ho 1994,
Santoni
et al
., 2001, Miller and Rifai 2004). As a result, fibre
reinforced soil consisting of polypropylene fibres have been
successfully used on embankment slopes in the US (Gregory
and Chill 1998) and in applications such as foundations for
sport pitches, horse racing tracks and access for secondary
roadways (Ibraim and Fourmont 2006).
The main objective of this study was therefore to investigate
the effect of including plastic strips from polyethylene shopping
