Dynamic response characteristics of dry and water-saturated schist under impact loading

Many geological engineering hazards are closely related to the dynamic mechanical properties of rock materials. However, most existing studies on the dynamic mechanical properties of rock materials were conducted on the hard rocks such as sandstone, granite, limestone, and marble, whereas soft rocks, such as schist, are less studied. Therefore, in this study, a series of triaxial impact tests were conducted on dry and saturated schist by employing a modified triaxial split Hopkinson pressure bar system to reveal the coupling effects of water, strain rate, and triaxial confining pressure on the mechanical properties of schist. The results show that schist is a type of watersensitive rock and the stress-strain curve of saturated schist has apparent ductility. The effects of strain rate on dynamic strain, deformation modulus and peak stress were analyzed. The results also show that the dynamic peak stress is affected by the combined softening effect and viscous effect of water under impact loading. Finally, it was found that the failure mode of schist belongs to typical axial tensile failure under uniaxial impact tests, and shear failure is the main failure mode under triaxial impact tests. With the increase in confining pressure, the failure modes of schist change from tensile failure to shear failure. This research can provide useful parameters for geological engineering hazard prevention in mountain areas.