Experimental study on volumetric strain development patterns and predictive modeling for saturated coral sands

Coral sand has better drainage conditions, and the drainage deformation of saturated coral sand under earthquake and wave load can easily cause damage to the seabed and nearby structures. Focusing on the properties of saturated coral sand and aimed at investigate the effects of fines content FC, relative density Dr and cyclic stress ratio CSR on its deformation characteristics, a series of cyclic drainage loading tests were carried out for its specimens on Nansha islands using a GDS dynamic triaxial instrument The test results show that, its development rate and the degree of deformation of cumulative volumetric strain εvp coral sand increase with the increase of FC and CSR, and decrease with the increase of Dr. The saturated coral sand εvp ~ N relationship curve shows two development modes of, cyclic-smoothness and cyclic-creep. The potential damage factor DP was introduced to characterize the influence of FC on the development pattern of εvp, and a DP×CSR ~ Dr framework was established to evaluate the strain development pattern of its volumetric. To characterize the effects of FC and Dr on its εvp ~ N relationship curve, the equivalent skeleton void ratio esk* was introduced, and it was found that there was a good correlation between εvp-s and esk* in both of its development modes, thus, a model for the development of volumetric strain in saturated coral sand under drainage cyclic loading conditions was established, which can well predict the development pattern of volumetric strain in saturated coral sand.