Layer Orientation Effect on Fracture Mode and Acoustic Emission Characteristics of Continental Shale

Based on the Brazilian tests of continental shale with different layer orientations, combined with AE monitoring, the influence of layer orientation on the anisotropy of mechanical properties, fracture mode, and fracture mechanism of continental shale was analyzed. The results show that the tensile strength and deformation at the peak stress decrease with the increase of layer orientation at a constant deformation loading rate of 0.06mm/min, and the splitting modulus decreases first and then increases. The tensile strength was 90 degrees > 60 degrees > 45 degrees > 30 degrees > 0 degrees, and the maximum and minimum tensile strengths were 5.154 MPa and 0.669 MPa, respectively. Under the action of splitting load, the samples with 30 degrees, 45 degrees, and 60 degrees layer orientations mainly undergo shear failure along the layer orientation, while the samples with 0 degrees and 90 degrees layer orientations undergo tensile failure. In addition, the crack propagation in the 0 degrees and 30 degrees samples penetrated the bedding. These characteristics have important reference significance for the study of the mechanism of hydraulic fracture communication, propagation, and activation of structural planes.