Effect of Lateral Load on the Mechanical Properties and Failure Modes of Sandstone Brazilian Discs during the Biaxial Splitting Test

To study the mechanical properties and failure modes of the Brazilian disc under biaxial splitting loading, different stress ratios (i) (axial stress:lateral stress) i = 1:1, 2:1, 3:1, 4:1, and & INFIN;:1 are experimentally applied in sandstone discs by a hydraulic servo-controlled testing machine equipped with a lateral loading device. Meanwhile, digital image correlation (DIC) and the FLAC3D are used to obtain the strain field and stress field evolution of the specimens. It was found that the presence of lateral pressure limits, the formation of horizontal tensile stress to varying degrees, and the axial peak loads decrease with the stress ratio. The failure modes that the rock discs underwent were shear failure, shear-tension mixed failure, and tensile failure as the stress ratio increased. The DIC results show that the maximum strain field gradually transitioned from the adjacent loading points of the discs to between two loading points in the axial direction with the stress ratio. In addition, the simulation results also demonstrated the transformation of the dominant stress in the stress field from tensile stress to shear stress with increasing lateral pressure.