# Experimental Study on Mechanical Properties of Mask-Improved Calcareous Sand
## 4 Conclusions  
The study investigated the effect of the mask on the mechanical behavior of calcareous sand through triaxial tests and also examined the enhancement of permeability and resistance to water erosion in calcareous sand via percolation tests. The significant application potential of this material was demonstrated, and the main findings can be summarized as follows:  
1. At a low content (0.9% by mass), an increase in mask content resulted in higher peak strength, internal friction angle, and ductility of the mixture, a reduction in the initial modulus, and suppression of dilatancy. This suggests that the mask has significant potential in enhancing the bearing capacity of calcareous sand roadbeds to resist shear deformation under dynamic vehicle loading.
2. The reinforcing effect of the mask on the soil matrix arises from the high friction at the mask-calcareous sand interface, which enhances the overall strength of the mixture by restricting the movement of soil particles during deformation. However, due to the mask's deformability, the surrounding calcareous sand undergoes rearrangement at the onset of shear, which leads to a reduction in the initial modulus of the mixture.
3. The incorporation of the mask can effectively inhibit the fragmentation of calcareous sand particles, with the optimal effect observed at a 0.3% incorporation rate. This suggests that the mask has promising potential for enhancing the long-term stability of steep-slope calcareous sand soil bodies.
4. The incorporation of the mask reduces the coefficient of permeability of calcareous sand, prevents particle loss, and, at a mask content of 0.3%, particle loss is substantially inhibited while the permeability of the specimen is only slightly reduced. In scenarios where both permeability and particle loss are critical (e.g., shallow foundations in areas with fluctuating water tables), calcareous sand particle loss is significantly reduced, thereby extending the structural lifespan.  
Conceptualization, L.Z. and J.Z.; methodology, J.Z.; validation, Z.Z. and J.Z.; formal analysis, Z.S.; investigation, Z.S.; resources, J.Z.; data curation, Z.S.; writing--original draft preparation, Z.S.; writing--review and editing, L.Z. and J.Z.; supervision, Z.Z. and B.L.; project administration, B.L.; funding acquisition, J.Z. and B.L. All authors have read and agreed to the published version of the manuscript.  
Figure 13: (**a**) Proportion of particle loss and (**b**) coefficient of permeability.  
**Funding:** This research was funded by Water Resources Science and Technology Program of Hunan Province, China (XSKJ2023059-45); the Natural Science Foundation project of Hunan Province, China (2023 JJ40332); the National Natural Science Foundation Project of China (NSFC) (52208341); and the 2023 Central Agricultural Machinery Research and Development, Manufacturing, Promotion, and Integrated Application Pilot Fund, China Project (Hunan Finance Department's Pre-(2023) No. 204 Document); the Key Scientific Research Project of Hunan Provincial Department of Education (23A0176).  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The original contributions presented in the study are included in the article; further inquiries can be directed to the corresponding authors.  
**Conflicts of Interest:** The authors declare no conflicts of interest.