Moisture Effects on the Undrained Dynamic Behavior of Calcareous Sand at High Strain Rates

Abstract The dynamic behavior of calcareous sand at high strain rates (HSRs), which is relevant to mining industry, aircraft wheel loading, and pile driving, is still not fully understood. To investigate the effects of the moisture content, 34 HSR tests and 26 low strain rate (LSR) tests were conducted on calcareous and silica sands using the split Hopkinson pressure bar (SHPB) technique with a rate ranging between 100 s−1 and 104 s−1 and using a mechanical testing and simulation (MTS) apparatus with a rate ranging between 10−5 s−1 and 10−1 s−1, respectively. It is found that the compression of unsaturated sand is almost larger than that of dry sand because the compressibility of particles and effective confining pressure change with moisture content. The dynamic stress–strain curve of unsaturated silica sand moves upward with moisture content at HSRs, but that of unsaturated calcareous sand is insensitive to moisture content. Compared with silica sand, calcareous sand reached its optimum capacity for energy absorption at lower stresses and energies. The energy absorption of unsaturated sand decreases with an increasing moisture content, while its transmitted load increases. To improve the cushioning properties of sand, a moderate water content is proposed.