Strain-Dependent Effects of Microplastic Contamination on the Strength and Modulus of Kaolin Clay

With wildfires occurring yearly in the United States, an increased risk of wildfire-induced microplastic contamination is common. Wildfires can generate microplastics from the thermal degradation of plastic materials found near urban areas, which then infiltrate soils as ash deposits. The contaminated soil’s geotechnical properties can differ depending on the contamination level compared to pure fine-grained soil. The effect of microplastics on clay particles and behavior is studied using a simple shear apparatus, with built-in bender element caps, at the California State University, Los Angeles. This paper examines the effects of polyethylene terephthalate (PET) contamination concentration of 10% by weight in kaolin clay samples. Introducing microplastics in the soil may result in changes in cohesion, friction angles, and shear modulus compared to kaolin samples, depending on the strain levels. By using the bender elements from the simple shear apparatus, the kaolin samples with microplastics showed higher stiffness at smaller strains.