Experimental and numerical study on dynamic mechanical behaviors of shale under true triaxial compression at high strain rate

High-energy gas fracturing of shale is a novel, high efficacy and eco-friendly mining technique, which is a typical dynamic perturbing behavior. To effectively extract shale gas, it is important to understand the dynamic mechanical properties of shale. Dynamic experiments on shale subjected to true triaxial compression at different strain rates are first conducted in this research. The dynamic stress-strain curves, peak strain, peak stress and failure modes of shale are investigated. The results of the study indicate that the intermediate principal stress and the minor principal stress have the significant influence on the dynamic mechanical behaviors, although this effect decreases as the strain rate increases. The characteristics of compression-shear failure primarily occur in shale subjected to triaxial compression at high strain rates, which distinguishes it from the fragmentation characteristics observed in shale under dynamic uniaxial compression. Additionally, a numerical three-dimensional Split Hopkinson Pressure Bar (3D-SHPB), which is established by coupling PFC3D and FLAC3D methods, is validated to replicate the laboratory characteristics of shale. The dynamic mechanical characteristics of shale subjected to different confining stresses are systematically investigated by the coupling PFC3D and FLAC3D method. The numerical results are in good agreement with the experimental data.