Performance Evaluation of Problematic Soils Reinforced with Plastic Wastes

Over the past years, because of the increase in the environmental and economic issues, there has been an increasing interest in the use of waste products for stabilization of problematic soils such as soft clays, expansive soils, liquefiable soils, etc. The use of plastic water bottles has been growing very fast and a huge amount of plastic wastes has been produced every year. The aim of this study is to recycle the empty plastic water bottles as a reinforcing material for the stabilization of problematic soils; Bedis beach sand and soft silty Tuzla clay. The laboratory tests were performed on reinforced soils with different plastic waste percentages: 0.5%, 0.75% and 1.0% of dry weight of soil and at two relative density states: 30% and 60%. For Bedis beach sand, direct shear box test was performed for determining the shear strength parameters and California Bearing Ratio, CBR test was performed for determining the bearing capacity of soil. For Tuzla soil, one dimensional swell and consolidation, unconfined compression, and California Bearing Ratio tests were performed. Test results indicated that reduction in the unconfined compressive strength of the reinforced Tuzla soil was obtained because of the reduction in the dry density of the reinforced soil. However, recycling plastic bottles as reinforcing material in the same soil improved the volume change behaviour. With only 0.75% plastic waste reinforcement, reduction in the swelling and the compressibility characteristics of the Tuzla soil was obtained. Keywords: California bearing ratio, cohesion, direct shear box, loose sand, recycling, shear strength, plastic waste.