Effect of inherent anisotropy and principal stress rotation on the cyclic response of calcareous sand

Abstract

Calcareous sand foundations or seabed face numerous challenges in complex marine environments. Among these, the coupled effects of principal stress rotation and inherent anisotropy on the cyclic properties of calcareous sand remain unclear. Therefore, this study utilized an inclined sand specimen preparation apparatus (ISSPA) to prepare specimens with different bedding angles α₃. Based on this, a series of principal stress rotation tests accounting for inherent anisotropy—also termed biaxial rotation of principal stress tests—were conducted. The test results indicate that pore pressure and deformation exhibit two distinct development patterns. Liquefaction resistance initially increases and subsequently decreases with increasing bedding angle α₃, while it decreases with increasing cyclic stress ratio (CSR). Specimens with a bedding angle α₃ of 45° demonstrate the highest resistance to liquefaction. Interestingly, the pore pressure at the strain turning point was approximately 0.83 times the mean effective pressure p′. Furthermore, both bedding angle α₃ and CSR significantly influenced the stress–strain relationship. Larger bedding angles resulted in a slower stiffness decay of calcareous sand under principal stress rotation. Based on the test results, mathematical models describing excess pore pressure Δu, generalized shear strain γ_g, axial shear modulus E_a, and damping ratio D_a were established.