Abstract
Understanding the anisotropic mechanical properties of rocks is crucial in rock engineering planning and execution. Layered structures, including foliation and bedding, introduce planes of weakness that profoundly affect the rock's mechanical response. This research aimed to examine the impact of foliation orientation, indicated by the dip angle (θ), and the strain rate (\(\dot {\varepsilon }\)) on the dynamic mechanical behaviour of the slate. To this end, dynamic compression tests were conducted on slate samples utilizing a split-Hopkinson pressure bar (SHPB). When the foliation is parallel to horizontal plane (θ = 0°), tensile mechanism dominates the failure mode. When the foliation planes take a dip angle to horizontal plane (θ = 30°, 45° and 60°), shear-sliding along foliation planes gradually dominated as the angle increased, resulting in shear-tensile failure. When the foliation planes are perpendicular to horizontal plane (θ = 90°), the sample primarily exhibits tensile splitting failure along foliation planes. Motivated by experimental results, we developed a constitutive model to characterize the damage process of foliated slate. The model assumes that the strength of microstructural units within foliated slate follows a Weibull distribution. To account for the effects of different dip angles and strain rates on the slate foliation planes' response, a dynamic loading viscous coefficient, η, is incorporated. The proposed model has precise physical meanings and proficiently illustrates the complete stress-strain process of the slate.