Abstract: The physical and mechanical properties of coral sand particles determine the macro mechanical behaviors of coral sand, which is closely related to several geotechnical engineering problems, especially those related to particle breakage. The apparent and internal structure characteristics of coral sand particles were studied by SEM and X-CT tests. It was found that the coral sand particles were porous. The porosity of coral sand particles with biological skeleton components was as high as 41%, while the porosity of coral sand particles formed by weathering and depositing was less than 20%. Most of the pores on the surface of the particles can be connected with the interior so that the gas can flow through the particles. The failure type of coral sand particles was closely related to the porosity. The coral sand particles with low porosity were broken into fragmentations step by step, similar to silica sand particles. The coral sand particles with high porosity were gradually compressed with the failure of skeleton. The failure of the skeleton was accompanied by the formation of fine detritus which did not detach from the skeleton until the particles were compressed into powder. The elastic modulus, yielding strength and crushing strength of circular, branched and flaky coral sand particles were determined by compression tests and statistical analysis. The correlations between particle strength and particle size was clarified, which provided parameter basis for studying the mechanical properties of coral sand. Furthermore, the stress-strain curves of yielding and crushing were exponentially distributed, which laid a foundation for further exploration of particle crushing characteristics in the future.

Key words: coral sand, porosity, particle crushing, crushing strength, stress-strain