3243
Utilization of waste copper slag as a substitute for sand in vertical sand drains and
sand piles
Utilisation des scories de cuivre en tant que substitut pour le sable dans des drains
et des colonnes de sable
Nawagamuwa U.P.
University of Moratuwa, Sri Lanka
Senanayake A.
University of Texas at Austin, USA
Rathnaweera T.
University of Calgary, Canada
ABSTRACT: Vertical sand drains are used as a method of expediting consolidation for ground improvement projects. Unfortunately,
the installation of vertical sand drains have become less economically viable due to the high costs and limited availability of good
quality sand. Particle size distribution analyses done on samples of waste copper slag obtained from the Colombo dockyard revealed
that its gradation was similar to that of sand, which meant that waste copper slag could potentially be used as a substitute for sand,
provided that it did not adversely affect the hydraulic conductivity of the resulting mixture. In this study, constant head permeability
tests were done on “sand-copper slag” mixes of varying proportions and it was shown that up to 50% copper slag by weight could be
added to sand without an appreciable loss in permeability. The performance of sand piles is dependent on strength and settlement
characteristics of the sand. Hence, consolidation tests and direct shear tests were also carried out on the “sand-copper slag” mixes to
explore how the mechanical properties of sand were affected by the copper slag.
RÉSUMÉ : Sable drains verticaux sont utilisés en tant que méthode d'accélérer la consolidation des projets d'amélioration des sols.
Malheureusement, l'installation de drains verticaux sable sont devenues moins rentables en raison des coûts élevés et une disponibilité
réduite de sable de bonne qualité. Analyses granulométriques effectuées sur des échantillons de scories de cuivre obtenu à partir des
déchets du chantier naval Colombo a révélé que sa gradation était semblable à celle du sable, ce qui signifie que scories de cuivre des
déchets pourrait être utilisé comme un substitut pour le sable, à condition que cela ne nuise pas la conductivité hydraulique du
mélange résultant. Dans cette étude, des essais de perméabilité constants ont été réalisés sur la tête "sable-laitier de cuivre" mélange
des proportions variables et il a été montré que jusqu'à scories de cuivre 50% en poids peuvent être ajoutés au sable sans perte notable
de la perméabilité. La performance des piles de sable dépend des caractéristiques de résistance et de règlement du sable. Ainsi, des
essais de consolidation et essais de cisaillement direct ont également été menées sur le sable-laitier de cuivre mélange d'explorer la
façon dont les propriétés mécaniques de sable ont été affectés par les scories de cuivre.
KEYWORDS: waste copper slag, vertical drains, sand piles,
1 PARTICLE SIZE GRADATION
Laboratory sieve analyses were conducted on the waste copper
slag. The material was first sieved through the No.4 (4.75mm)
sieve to remove coarse particles which do not fall within the
particle size range of sands. The results showed that the copper
slag had a very small range of particle sizes. The material could
be categorized as “poorly graded” according the USCS (C
u
= 2.5
and C
c
= 0.9).
The waste copper slag was mixed with a poorly graded sand
(C
u
=3, C
c
=1.1) in proportions of 10%, 20%, and 40% by
weight and tested how the geotechnical engineering properties
of the sand would be affected.
The results of sieve analysis test conducted on the copper-
sand mixes are shown in figure 1. It can be observed that the
gradation curve is not greatly affected by the addition of waste
copper slag. The only apparent change is a slight shift in the
curves towards the right.
Figure 1: Particle Size Distribution Curves
2 HYDRAULIC CONDUCTIVITY
A poorly graded material will have a high void ratio as
compared to a well graded material. Whilst this may be a
undesirable attribute in many engineering applications, it can be
an advantage if the material is to be used for sand drains. The
purpose of sand drains is to provide a mechanism to expediting
the dissipation of excess pore water pressures created in soil
