Experimental Study on the Mechanical Behavior of Sandy Soil Reinforced by Disposable Face Mask Chips under Different Stress Paths

Since 2020, with the global spread of major respiratory infectious diseases, such as COVID–19, the demand and consumption of personal protective equipment, such as masks, have increased dramatically worldwide. The environmental pollution caused by numerous waste disposable face masks has gradually attracted people's attention. In this study, the mechanical properties of mask–chip–reinforced soil are evaluated from a new perspective, through the uniaxial, biaxial, conventional triaxial, and true triaxial compression tests on reshaped sandy soil samples mixed with different contents of mask chips. The experimental results show that the mechanical properties of the sandy soil can be improved by the mask chips. With the proper content of mask chips, the failure strength is substantially improved, and the failure of soil is delayed. Meanwhile, the strength and stiffness are significantly affected by the stress path and the content of mask chips, even if the soil samples with the same mask–chip content can also show different mechanical properties under different stress paths. Additionally, the mechanical properties of soil are not necessarily improved constantly with the increasing content of mask chips. The failure strength of sandy soil samples under conventional and true triaxial stress paths decreases when the mass content of mask chips exceeds 0.3% and 0.5%, respectively. This study confirms the potential of mask chips applied to subgrade, slope, and other engineering construction fields in a sustainable way. © 2023 by the authors.

Experimental study on the monotonic mechanical behavior of completely decomposed granite soil reinforced by disposable face-mask chips.

In response to the global outbreak of the coronavirus pandemic (COVID-19), a staggering amount of personal protective equipment, such as disposable face masks, has been used, leading to the urgent environmental issue. This study evaluates the feasibility of mask chips for the soil reinforcement, through triaxial tests on samples mixed with complete decomposed granite (CDG) and mask chips (0%, 0.3%, 0.5%, 1%, 5% by volume). The experimental results show that adding a moderate volumetric amount of mask chips (0.3%-1%) improves the soil strength, especially under high confining pressure. The optimum volumetric content of mask chips obtained by this study is 0.5%, raising the peak shear strength up to 22.3% under the confining stress of 120 kPa. When the volumetric content of mask chips exceeds the optimum value, the peak shear strength decreases accordingly. A limited amount of mask chips also increases the elastic modulus and makes the volumetric response more dilative. By contrast, excessive mask chips create additional voids and shift the strong soil-mask contacts to weak mask-mask contacts. The laser scanning microscope (LSM) and scanning electron microscope (SEM) images on the typical samples demonstrate the microstructure of mask fibers interlocking with soil particles, highly supporting the macro-scale mechanical behavior.