Anisotropic behaviors of calcareous sand dependent on loading direction and initial shear stress.

Calcareous sand has been a suitable unbound granular filler in island reef engineering. Given its unique microstructure and the complex loading situation in practical engineering, anisotropy is a crucial factor that cannot be ignored. In light of this, we conducted a set of hollow cylindrical shear tests to explore how the loading direction and initial shear affect the anisotropic behaviors of calcareous sand, with Silica sand as the control material. A remarkable finding is that calcareous sand is more anisotropic than silica sand due to its irregular particles, as evidenced by a greater variation in internal friction angle(φ f) and stress ratio at failure(M f) with influencing factors. To accurately represent these variations caused by anisotropy, a parameter for quantifying anisotropy was found. The dependence of the two influencing factors on M f was formulated based on the parameter. The formulated M f was then applied to the UH model, and the predicted and experimental results of the shear response were compared to evaluate the model performance. [ABSTRACT FROM AUTHOR]