Sustainable Ground Improvement Using Waste Plastic Bottle Mattresses Beneath Strip Footings

The persistence of plastic waste, particularly polyethylene terephthalate (PET) bottles, poses a major environmental concern due to its non-biodegradable nature. Repurposing these materials as ground improvement elements provides an environmentally friendly and cost-effective alternative to traditional geosynthetics. This study investigates the use of waste plastic bottle mattresses as reinforcement for sandy subgrades supporting strip footings. A series of physical model tests was conducted to evaluate how variations in mattress embedment depth, width, and height influence foundation performance. The results showed that the inclusion of bottle mattresses consistently improved both the load-bearing capacity and the initial stiffness of the foundation system. The degree of improvement was closely tied to the interaction between the stress influence zone and the confinement effect of the reinforcement, with efficiency stabilizing beyond certain geometric limits. The outcomes of this study provide practical guidance for optimizing reinforcement geometry in shallow foundation systems and underscore the value of integrating recycled materials into geotechnical design frameworks.