Dynamic mechanical response and particle breakage characteristics of calcareous sand

Calcareous sand is widely used as shallow foundations, where the mechanical behavior of calcareous sand under impact loading would be affected by the particle sizes and moisture contents in the foundation. Herein, a series of impact loading tests were carried out with a modified Split-Hopkinson Pressure Bar (SHPB) system to investigate the mechanical characteristics of calcareous sands subjected to varying particle sizes and moisture contents. In particular, a new specimen chamber in the SHPB system was proposed to hold the sand specimen. Subsequently, several impact tests were conducted on calcareous sands with different particle sizes, where the uniform sizes of 0.074-0.5, 0.5-1.0, 1.0-2.0, and 2.0-3.0 mm and moisture contents from 0 to 16 % were adopted. Afterwards, the effects of the strain rates such as 165 s-1, 214 s- 1, and 256 s- 1 were studied on mechanical and particle breakage behaviors of the calcareous sands. The impact response, particle-size distribution curves and relative breakage curves were then analyzed. Results indicated that the peak stress decreased with the increase of moisture contents in medium- and coarse-sized calcareous sands. The effect of moisture content on the particle breakage of unsaturated calcareous sand decreased with increasing particle sizes. The relative breakage has an exponential relationship with the particle sizes of calcareous sand, which was expressed by an effective diameter. The outcome of this study indicated that the energy dissipation effect of calcareous sand protective cushion was effectively improved by appropriate moisture content of calcareous sand.