Flowability of Saturated Calcareous Sand

The potential for damaging flow liquefaction failure of calcareous sands subject to seismic, wave, or other dynamic loading is of increasing importance owing to its predominance along coastal areas and increased use as a fill material. Undrained cyclic triaxial tests were performed on saturated calcareous sand specimens prepared with different relative densities and subjected to various effective confining pressures to study the flowability of viscous, liquefied calcareous sand. The cyclic shear stress-strain rate relationship for the saturated calcareous sand specimens transitioned from an elliptical shape to a dumbbell shape as excess pore pressures accumulated under cyclic loading. The dumbbell-shaped relationship demonstrates that the saturated calcareous sand exhibited low shearing resistance and high fluidity under elevated excess pore pressures for certain conditions evaluated. The average flow coefficient, defined as the maximum shear strain rate triggered by the unit average cyclic shear stress, and the flow curve describing the flowability, of the saturated calcareous sand are used to quantify the cyclic failure potential of the calcareous sand. The relative density and cyclic stress ratio has a significant influence on the average flow coefficient: the smaller the relative density and larger the cyclic stress ratio, the smaller the number of cycles to failure. In contrast, the effective confining pressure has little effect on the magnitude of flow potential or number of cycles to triggering flow-like behavior.