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

Abstract

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(φf) and stress ratio at failure(Mf) 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 Mf was formulated based on the parameter. The formulated Mf was then applied to the UH model, and the predicted and experimental results of the shear response were compared to evaluate the model performance.