The effect of drying and wetting cycles on the mechanical properties and particle breakage of carbonate sand

For islands in marine environments, groundwater levels vary due to the influence of tides. As a result, the external environment of backfilled carbonate sands on islands alternates between dry and wet conditions. In this paper, a series of one-dimensional compression tests and direct shear tests were carried out to examine the compression characteristics, shear strength and particle breakage of carbonate sand from the Xisha Islands subjected to drying and wetting cycles. Drying and wetting cycles dramatically increased the compressibility and reduced the shear strength of the carbonate sand. Based on the test results, a modified compression model was suggested to consider the effect of drying and wetting cycles, and the influence of drying and wetting cycles on shear strength was also presented. Sieving test results showed that the carbonate sand particles were more prone to crushing under the influence of drying and wetting cycles, which could be the main reason for the changes in the mechanical properties of the carbonate sand. In both compression and shear tests, there was a good linear relationship between relative breakage and drying and wetting cycles, as well as between fractal dimension and drying and wetting cycles. However, the relationship between fractal dimension and relative breakage differed between the two tests, suggesting that particle breakage evolves according to different modes under different stress paths. The changes in the mechanical properties and particle breakage of carbonate sand under drying and wetting cycles warrant the attention of engineers.