Undrained cyclic resistance and stiffness of anisotropically consolidated calcareous sand

Calcareous soil deposits serve as crucial foundation materials for various structures such as oil platforms, breakwaters, and offshore transportation infrastructures. These deposits often experience anisotropic stress conditions and endure initial static shear stress before undergoing cyclic loading during their service period. This study conducted a series of cyclic triaxial tests to explore the impact of anisotropic consolidation on the undrained shear characteristics of calcareous sand sourced from the South China Sea. Two distinct mechanisms of strain development, namely the cyclic mobility and residual deformation accumulation, were identified during the cyclic failure of the calcareous sand. The findings reveal that anisotropic consolidation can either augment or diminish cyclic resistance and stiffness, depending on the relative density of the sand. A comparative analysis with Toyoura sand, possessing a similar grading curve under identical testing conditions, highlights intriguing disparities. Despite being marginally superior to Toyoura sand under isotropic consolidation, calcareous sand exhibits relatively lower resistance when anisotropically consolidated to a significant static shear stress. Additionally, analysis of the tested calcareous sand – which possesses the lowest uniformity coefficient among the compared materials – reveals a greater susceptibility to cyclic liquefaction than other calcareous sands of diverse origins, highlighting how the role of static shear is inherently material-dependent.