Study on the relationship between fractal dimension and particle fragmentation for marine coral sand under impact load

As a subsoil for many offshore structures, marine coral sand can encounter various impact loads, resulting in particle fragmentation. The "fractal theory" is an excellent method to quantify particle fragmentation. However, the relationship between the fractal dimension and relative breakage as well as its influencing factors are somewhat limited for coral sand under impact loads. Therefore, this paper systematically investigates the fractal behavior of a classic type of coral sand in the South China Sea through a series of impact load experiments. The experiment results show that the gradation curve of the coral sand under impact loading exhibits evident fractal characteristics after fragmentation, with the fractal dimension increasing with increasing fragmentation. And the ultimate fractal dimension is independent of the particle size and uniformity coefficient. Therefore, taking the ultimate fractal dimension as an ultimate state of particle fragmentation, a relative breakage index based on the relationship between the original, current, and ultimate fractal dimensions is proposed. These results can support more efficient and accurate predictions of particle fragmentation, thus promoting the safer design and con-struction of offshore engineering in coral sand.