Estimation of coefficient of earth pressure at rest for coral sand considering the effect of density and stress

The coefficient of earth pressure at rest (K₀) is a crucial parameter in geotechnical design. In this study, coral sands with various initial relative densities were subjected to K₀ consolidation tests and consolidated-drained triaxial compression tests to investigate the impact of the relative density, stress level, and particle breakage on K₀. Based on the Mohr–Coulomb failure law and experimental data, a formula for estimating K₀ related to the effective stress and effective friction angle was proposed. The results revealed that the K₀ of coral sand decreased with an increase in effective stresses, while the impact of the initial relative density on K₀ was more obvious. At the same effective stress, the smaller the initial relative density was, the larger the K₀ can be. In the tested stress range, minimal particle breakage was observed during the K₀ consolidation, whereas a greater degree of particle breakage occurred during triaxial shear. This particle breakage has the potential to undermine the stress-dilatancy and interparticle locking characteristics in coral sands, leading to a diminished effective friction angle and potentially affecting K₀. The proposed formula for estimating K₀ can be expressed as a function of the effective stresses and effective friction angle, and the effect of initial relative density on K₀ can be reflected by the function parameters. This formula provides a reasonable estimate of the K₀ value for coral sand within a certain range of relative densities and stress levels. Furthermore, it demonstrates favorable applicability to other types of granular soils, such as quartz sand and rockfills.