Effect of state evolution on the mechanical characteristics of coral sand and associated constitutive model

The integration of state-dependent concepts into the classical critical state framework has significantly enhanced the ability to describe the macroscopic mechanical properties of terrestrial sandy soils. However, the complex physical properties of coral sand make it difficult to describe its mechanical response within this framework. In particular, the pronounced crushability and irregular morphology of coral sand (also known as calcareous sand) lead to the critical state line being strongly dependent on the initial density, which contradicts the assumptions of classical critical state theory. To overcome this limitation, this study extensively investigates the effects of density and gradation on the evolution of its critical state. On this basis, a simplified constitutive model, SANISAND04-St, is developed by incorporating the established state-evolution law into the classical SANISAND04 framework. The comparisons between laboratory results and the numerical predictions from SANISAND04-St indicate that the proposed model is effective and validate the feasibility of the state-evolution law presented in this study. Overall, this study represents a meaningful attempt to extend the classical critical state soil mechanics to sandy soils with complex properties.