Utilization of waste copper slag as a substitute for sand in vertical sand drains and sand pile

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.