Deformation and fracture of rocks due to high-speed liquid impingement

The paper reports on the deformation and fracture of four rock materials and two cementitious materials due to the impingement of simulated liquid drops at velocities up to 900 m/s. For hard materials, the damage appeared in the form of an undamaged central region surrounded by rings of discrete microcracks. The size of the undamaged zone corresponded to the theoretical contact diameter for low and medium impact velocities, whereas the outer ring size corresponded to the simulated drop diameter. For soft materials, crack formation was obliterated by features of plastic flow. An elastic-plastic transition criterion was derived to explain these different types of response. Crack ring diameter increased as impact velocity increased. However, for rather non-homogeneous materials this relationship was very weak. Failure due to lateral jetting could be noted and was found to contribute significantly to the damage. Material was removed by two different modes: 'drilling mode' and,chipping mode', respectively. The first mode applied to soft and porous materials, namely limestone and sandstone, whereas the second mode applied to rather dense and brittle materials, namely granite and feldspar.