Atmospheric effects on high-velocity impact cratering in porous sandstones

Granular geomaterials feature varied porosity and may possess pore fluids. The interactions between grains, pores, and pore fluids affect the impact dynamics in the material such as the cratering efficiency, ejecta kinetics and crater morphology. In this study, we conduct experimental analyses of high-velocity projectile impacts on sandstone to understand the effect of porosity and air pressure on the behaviour of porous geomaterials during impact. Our results show that different target porosities feature separate trends in crater morphology: Impact under air pressure results in larger crater diameters in low porosity sandstone but smaller crater diameters in sandstone of higher porosity. These results further highlight the significance of studying the relationship between grains, gas and pore spaces to understand the evolution of failure in porous rocks.