Effect of plastic fines on over consolidated mining sand

In-situ Malaysian soils in tin mining areas usually occur as mixtures of sand and clay in widely varying proportions. Their engineering behaviour is different from that of clean mining sands. Natural soils are often in a structured and over consolidated state. It was found that the rate of loss of pre-consolidation history in sand is much faster than that in clay. This paper addresses the effects of plastic fines on the shear strength behaviour of over consolidated mining sands. An experimental investigation on samples of reconstituted clean mining sand containing different proportions of plastic fines was carried out. The samples were subjected to undrained triaxial compression tests under various levels of mean effective consolidation stress and unloaded to 100 kPa during shearing to achieve the OCR required. The stress-strain-pore pressure response, peak strength and soil stiffness were measured and evaluated for each plastic fines percentage in the over consolidated soil samples.