Mechanical Characteristics and Particle Breakage of Calcareous Sand under Quasi-One-Dimensional Impact Load

Calcareous sand, a type of marine sediment formed from the skeletal remains of marine life, exhibits unique characteristics such as high porosity and fragility due to its biological origin. Particle breakage is a key attribute of calcareous sand. Given that foundations on calcareous sand islands encounter various types of loads, including pile driving, aircraft loading, earthquakes, and tsunamis, it is imperative to investigate its mechanical properties and particle breakage under high strain rates. This study focuses on assessing the dynamic mechanical properties of calcareous sand under quasi-one-dimensional impact loads using split Hopkinson pressure bar (SHPB) tests. Three particle sizes of calcareous sand with different water contents, strain rates, and relative densities were examined. The particle fragmentation degree of each sand sample was also analyzed quantitatively. The results indicated that stress–strain curves progress through an elastic phase with rapid elevation, followed by a plastic stage with a slower increase under various factors. Within the plastic phase, there are multiple instances of stress drops and recoveries. The stress–strain curves generally decrease as particle size increases, concurrent with an increase in particle breakage. Moisture content has minimal impact on the stress–strain curve; a higher moisture content does correspond to reduced particle breakage. Both the maximum strain and peak stress increase as the strain rate increases, resulting in a higher relative crushing rate. The difference between stress–strain curves under different relative densities diminishes as particle size increases, and greater relative density leads to reduced particle breakage. Functional relationships among peak stress and strain rate, relative fragmentation rate and water content, strain rate and relative density, as well as relative density and peak stress are also established.