Compression responses and particle breakage of calcareous granular material in reclaimed islands

Calcareous gravelly sand (CGS) is a highly compressible and easily breakable granular geomaterial widely used to fill the island reef foundation. In this study, a series of confined compression tests were conducted on CGS, and the particle breakage of CGS was quantitatively assessed. The results showed that the power function model was more suitable for describing the stress-strain relationship of CGS under confined compression than the hyperbolic and Gunary models. The yield stress of CGS was distributed within the range of 1.89-2.45 MPa, which was significantly smaller than that of terrigenous quartz sand. The compression modulus of CGS increased with increasing relative density (Dr); however, it first increased and then decreased with increasing nonuniform coefficient (Cu). The compression behaviors of CGS after the yield point were mainly determined by particle breakage. The CGS sample, which had experienced more serious particle breakage, was compressed to a more compact state under vertical stress. The relative breakage ratio of CGS decreased with increasing Dr, whereas it first increased and then decreased with increasing Cu. The changes in the fractal dimension and gradation parameters of CGS before and after testing were also evaluated. The particle breakage mechanism of CGS during confined compression was revealed based on the changes in the mass fraction of different particle groups before and after testing.