# Experimental Study on Mechanical Properties of Mask-Improved Calcareous Sand
###### Abstract  
Due to the widespread prevalence of respiratory diseases such as COVID-19 and H1N1, the use of disposable masks has increased significantly. Consequently, the environmental issues arising from their accumulation have become increasingly severe. This study, therefore, aims to investigate the potential of using masks as soil reinforcement materials. This study conducted triaxial and seepage tests on mask-calcareous sand mixtures with varying ratios to examine the effects of mask content on the strength, modulus, particle fragmentation, and permeability coefficient of calcareous sand, as well as the influence of different mask sizes on shear strength and shear dilation. The results demonstrate that with an increase in mask content, the peak stress ratio of the mask-calcareous sand mixture increases by 4% per level, and the internal friction angle rises by approximately 1.6% per level. Conversely, water permeability and shear swelling are reduced, and particle loss decreases by over 70%. The reinforcing effect of the mask is attributed to the high friction between the mask and the calcareous sand at the contact interface, which restricts the movement of soil particles during deformation, thereby enhancing the overall strength of the mixture. Among the three mask sizes, the smallest mask-calcareous sand mixture exhibited the greatest improvement in shear strength, and the shear shrinkage effect was more pronounced. This indicates that particle size also significantly influences the mechanical properties of the mixtures. The reinforcing effect of the mask on the soil results from the high friction at the interface between the mask and the calcareous sand. When the soil deforms, the mask enhances the overall strength of the mixture by restricting the movement of soil particles. Considering the impact of masks on the performance of calcareous sand, it can be concluded that the optimal mass content of masks is 0.3%. This study offers a new perspective on the reuse of discarded masks in civil engineering applications. Keywords: triaxial test; particle breakage; volumetric strain; waste mask; calcareous sand; shear behaviors +
Footnote †: journal: Applied Sciences
treatments are costly, require long reaction times, and necessitate high temperatures or pressures as reaction conditions [3]. Landfilling of discarded masks causes them to migrate randomly under the influence of rainwater, occupying land [4]. Incleration releases large amounts of toxins and carbon dioxide [5]. These suboptimal waste disposal methods have resulted in a significant accumulation of discarded masks [6]. Disposable medical masks take hundreds of years to fully degrade in nature [2], This will impose a significant environmental burden [7; 8]. Therefore, identifying an effective large-scale disposal method for discarded masks has become an urgent global issue. Masks can be considered as special flexible fiber materials, similar to those often used to enhance the engineering properties of soils. Work on this area started in the 1980s, when [PERSON] [9] proposed that fiber reinforcement technology can improve the mechanical properties of soil. Subsequently, scholars found that the incorporation of fibers can improve the shear strength and internal friction angle of soil [10], reduce the swelling of granular soil during shearing [11], and enhance the ductility of the specimen [12]. Therefore, masks should also possess the potential to enhance the mechanical properties of soil. [PERSON]'s [13] research demonstrates that even simple heat treatment can fulfill the requirements for engineering environmental safety. Calcareous sand represents a potential material source for the construction of offshore structures, including wind turbines, oil platforms, terminals, land reclamation, and artificial islands.