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New Replacement Formations on Expansive Soils Using Recycled EPS Beads
Remplacement sur les sols expansifs en utilisant des perles EPS
Abdelrahman G.E.
Civil Engineering Department, Faculty of Engineering, Fayoum University, Egypt
Mohamed H.K.
Soil Mechanics and Geotechnical Engineering Institute, Housing and Building National Research Center (HBRC), Egypt
Ahmed H.M.
Civil Engineering Department, Faculty of Engineering Cairo University, Egypt
ABSTRACT: One of the main problems encountered in constructing foundations on clays is volume change independent of loading
caused by swelling of the soil. When the swelling is obstructed, large swelling pressures arise and that can cause damage to structures.
This study examines the role of recycled expanded polystyrene (EPS) beads which is mixing with replaced soil in accommodating soil
expansion and hence reducing swelling pressures on structures foundation. Laboratory tests are presented on the formation of
expansive soil using Bentonite clay. Laboratory model was used to measure the decrease of the swelling, using replacement material
which formed of blending sandy soil with recycled (Expanded Poly-Styrene) EPS-beads. The effect of different compositions and
different ratios between EPS-beads, and sand as a replacement soil on the expansive soil (Bentonite powder, PI=95.4%, and G
s
=2.55)
which had free swell equal to 96.7% were studied. Results so far show that the EPS beads mixed with sand significantly reduces the
volumetric change of the expansive soils. The parametric study showed that increasing EPS beads percentage in the replacement soil
decreases bearing capacity and dry density γ
d
, and increases OMC while for the Bentonite free swell decreases and settlement
increases. Increasing footing breadth increases swelling and settlement. With increasing replacement layer thickness and beads
density, the swelling and settlement decrease.
RÉSUMÉ : Un des principaux problèmes rencontrés dans la construction des fondations sur des argiles est le changement de volume
indépendant de chargement provoqué par le gonflement du sol. Lorsque le gonflement est obstrué, les grandes pressions de
gonflement surviennent et peuvent causer des dommages aux structures. Cette étude examine le rôle du polystyrène expansé recyclé
(EPS) des perles qui est le mélange avec le sol remplacé en accueillant l'expansion du sol et donc la réduction des pressions sur le
gonflement de fondation des structures. Des essais en laboratoire sont présentés sur la formation des sols expansifs avec de l'argile
bentonite. Modèle de laboratoire a été utilisé pour mesurer la diminution de l'enflure, l'utilisation du matériel de remplacement qui a
formé de l'assemblage avec des sols sablonneux recyclés (Expanded Poly-Styrène) EPS-perles. L'effet de différentes compositions et
différents ratios entre les EPS-perles, et le sable du sol comme un remplacement sur le sol expansive (bentonite en poudre, PI =
95,4%, et GS = 2,55), qui avait sans égale gonfler à 96,7% ont été étudiés. Les résultats obtenus jusqu'ici montrent que les perles EPS
mélangés avec du sable réduit considérablement le changement volumétrique des sols gonflants. L'étude paramétrique a montré que
l'augmentation des EPS perles de pourcentage dans le sol de remplacement diminue la capacité portante et la densité sèche γd, et
augmente OMC alors que pour la bentonite diminue la houle libres et augmente de règlement. L'augmentation de la largeur de
fondation augmente l'enflure et de règlement. Avec une épaisseur de remplacement couche augmente et la densité des perles, l'enflure
et la diminution de règlement.
KEYWORDS: Recycled expanded polystyrene, beads, expansive soils, swelling, sand, Bentonite.
1 INTRODUCTION
Problems related to expansive soils exist worldwide. Many
buildings, light structures, highways, railways, airport slabs,
water channels, pipelines, earth retaining walls, dams and
bridges are damaged by expansive soils. One of the main
problems encountered in constructing foundations on clays is
volume change independent of loading caused by swelling and
shrinkage of the soil. When the swelling is obstructed, large
swelling pressures arise and that can cause damage to structures.
There are many conventional treatments available for control of
these problems. These include soil replacement with
compaction control, moisture control, surcharge loading and
thermal methods (Chen, 1988; Nelson and Miller, 1992).
However, these methods have their own limitations with regards
to their effectiveness and costs.
Expanded polystyrene (EPS) is a cellular polymeric material
commonly used as a packaging medium for a variety of
consumer appliances and electronic equipment. It is a
lightweight material with a very low density (0.10 -0.20 kN/m
3
)
.Due to its convenience and low cost, EPS usage is increasing in
the consumer market. That in turn results in a continuing
increase in the availability of waste EPS products. Because of
their lightweight and bulk nature, the waste EPS products
occupy a substantial area of the landfill. Unlike other organic
materials, EPS is not decomposable or biodegradable. Because
of these problems, the European Union has restricted the
disposal of EPS into landfills and set recycling targets (PPW
Directive, 2005; UNEP, 2000). These impositions have forced
manufactures to look for alternative reuse and recycle options.
There are many recycling options available like thermal and
compression methods. However, possible contamination of the
products while in transportation and their limited usage make
some of the products unsuitable for recycling. Hence there is a
need to try other innovative applications for the bulk utilisation
of waste EPS.
Since its inception, EPS composite soil has attracted the
interests of many researchers. A few papers have been
published regarding using EPS composite soil in reducing
swelling pressures on structures foundation and behind retaining
walls. Illuri & Nataatmadja (2007) and Illuri (2007)
investigated the use of recycled EPS as a partial soil
replacement and swell modifier for expansive soils. Artificially
prepared expansive soils were manufactured in the laboratory
by mixing fine sand with sodium bentonite of various
proportions. Recycled EPS beads were mixed with these soils
