Utilization of single-use face masks for sand reinforcement: insight from experimental and numerical studies

In the context of COVID-19 rampant worldwide since 2019, the stock of disposable single-use face masks (SUFMs) has climbed steadily, which results in an urgent worldwide environmental problem. This study aims to propose a potential method for processing and utilizing SUFMs in soil reinforcement to address the significant volume of discarded masks, thereby contributing to geotechnical engineering construction. Hence, in this study, SUFMs were prepared into three geosynthetic forms considered potential candidate options: fibers, geotextiles, and geocells. The performance of geosynthetics-reinforced sand was assessed by the static triaxial tests by considering the fibers reinforcement with the content of 0.25% and 1.0%, single-layer and three-layer geotextiles reinforcement, and geocells reinforcement. A series of numerical simulations were also conducted to investigate the failure mechanisms of various reinforced forms. The experimental results show that the three geosynthetic types can improve the sandy soil's shear strength and apparent cohesion. The SUFMs fibers reduce the elastic modulus due to the higher compressibility of the SUFMs, while the elastic modulus of geotextile and geocell-reinforced soil samples is elevated. The numerical analysis results indicate that the SUFMs fibers and geotextiles can limit the lateral deformation and spread the shear stress over a wider area through the interface friction between geosynthetics and soil. On the other hand, the vertical walls of geocells can provide direct lateral restraint, and the reinforcement effect is more direct and better.