Fractal characteristics of particle breakage on the coral sands–structure interface during ring shear tests

Abstract

Particle breakage at coral sands–structure interface is common in marine geological environments and is critical to the stability of geotechnical structures. However, due to the knowledge gap regarding the relationship between structure roughness and coral sand particle breakage, previous studies have not provided a clear understanding of this phenomenon. To address this gap, we conducted ring shear tests to investigate the evolution of the fractal dimension of particle breakage and its dependence on structure surface roughness and vertical stress based on fractal theory. The results show that both the roughness of the steel plate simulating the structure surface in the ring shear test and the particle size of coral sand have significant impacts on the evolutions of particle breakage and morphology at the contact interface. In detail, the particle size distributions (PSDs) of coral sands after shearing have obvious self-similarity and converge to the limit distribution state, especially when the sands contain more large particles. When the steel plate is smooth, the fractal dimension of the broken coral sand is relatively low, which indicates an early stage of fractal dimension development. Moreover, the relationship between the fractal dimension and vertical stress exerted on a rough steel plate can be approximately described using a second-order polynomial function. Moreover, there exists a critical vertical stress that corresponds to the maximum fractal dimension for each kind of coral sand in our tests. The particle breakage rates of coral sand samples on smooth steel plates are substantially lower than those on rough steel plates.