Coral sand is a type of marine biogenic granular material with extremely high calcium content. From the microscopic viewpoint

coral sand grains are characterized as highly angular

irregular in shapes and crushable. One-dimensional creep tests were conducted on coral sand under very high pressure to investigate the evolution of particle size distribution and change of particle shapes caused by particle breakage. Benefited from particle size analysis and shape evaluation with high speed dynamic image analysis apparatus

the evolution of particle shape along with stress was analyzed statistically

and shape factors including aspect ratio

sphericity and convexity increase with increasing pressure. Shape factors for particles with different sizes tend to reach a same value

which illustrated that the morphology of particle after breakage is scale independent and self-similar in this wide range of sizes. This paper analyzed the fractal feature after particle breakage

and found that the fractal dimension increases with increasing vertical stress

and eventually reaches the fractal ultimate breakage (D=2.5). This paper calculated the relative breakage by using Hardin’s and Einav’s methods

and found that relative breakage is increasing along with increasing pressure. The relative breakage is an exponent function with the pressure

which could be used to predict the relative breakage if the material and pressure are known. The increasing tendency with time is not obvious

because particle breakage is majorly caused by compression instead of creep.