Recycling plastic waste from water bottles has become one of the main challenges worldwide. The aim of this study is to recycle empty plastic water bottles as reinforcing material for the improvement of sandy soil. The laboratory tests were performed on both natural and reinforced sands with different plastic waste percentages: 0, 0.5, 0.75 and 1.0 of the dry weight of sand at relative density states of 30% and 60%. Direct shear box and the California Bearing Ratio, CBR tests were performed to determine the effect of the plastic waste on the shear strength and the penetration resistance of the reinforced sand. Test results indicated that plastic waste reinforcement contributed to the improvement of the shear strength and the CBR number of the reinforced sand. Higher shear strength and higher penetration resistance were obtained with plastic waste reinforcement. The optimum percentage of plastic waste required for enhancing the shear strength and the CBR number was found to be 0.75%. With the optimum percentage of plastic waste, the improvement in the shear strength and the penetration resistance of the reinforced sand increased to at least 9% compared to natural soil at relative density states of 30% and 60%.
Stone columns were found to be effective, economical and widely-used ground improvement technique in soft grounds. It is important to understand the behavior of stone columns when they are installed in layered soils. This paper presents results from a series of small scale laboratory model tests carried out in unit cell tank to investigate the behavior of floating and end bearing stone columns in layered soils with and without encasement, consisting of loose sand overlying a soft soil. Tests were conducted with loading only the stone column area to estimate the limiting axial capacity of stone column. Laboratory tests were carried out on a column of 10 cm diameter surrounded by layered soil. Test results indicated that the bearing capacity of layered soil has been improved in all cases of stone column applications. The non- encased floating stone columns gave better results than non-encased end bearing stone column. The inclusion of geotextile encasement resulted in further improvement of layered soil and the encased floating stone column had superior bearing capacity improvement.
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