Dynamic Compression Response of Dry and Moist Coral Sands at High Strain Rates

Abstract High strain rate (HSR) loading conditions are often encountered during mining activities, compaction, pile driving, aircraft wheel loading, etc. Moreover, the adverse effects of particle breakage in coral sand are now well known and no longer debated. Thus, investigating the mechanical response of crushable coral sands under the HSR conditions becomes crucial. In this study, efforts are made to understand the dynamic behavior of coral sands under HSR compression employing a series of modified split Hopkinson pressure bar (MSHPB) tests. The influence of various factors such as strain rate, gradation, and moisture content on axial stress–strain curves, compressibility, energy absorption, and transmissibility is studied. Furthermore, particle breakage characteristics of coral sands are also quantified utilizing the particle size distributions (PSDs) before and after the test. X-ray computed tomography is used to determine the shift in PSDs caused by impact loads. The test results show that, similar to silica sand, the axial stress–strain curves of coral sand also show lock-up zones under HSR conditions. Furthermore, the nature of axial stress–strain curves is highly dependent on the gradation. At low water content, moisture has softening effects on the dynamic compression response of coral sand. However, the HSR response of moist coral sand with high water content showed hardening when compared to that of dry sand. Finally, it has also been observed that, for a given strain rate, particle breakage in coral sands reduces with a drop in the mean grain size of the specimen or an increase in the moisture content.