Mechanical and Energy Evolution Characteristics of Sandstone under True Triaxial Cyclic Loading

To study the mechanical and energy evolution characteristics of sandstone under true triaxial cyclic loading, a test with different intermediate principal stress loading was conducted using rock disturbance unloading system. The influence axial load on deformation, evolution, macroscopic failure in systematically analyzed, damage law revealed. Results showed that mode compression changed from tension–shear composite to tension failure. Grading σ1 greatly influenced maximum strain ε1 minimum ε3 but had little ε2. Under same σ2 condition, input elastic σ1, σ2, σ3 directions increased nonlinearly. conditions, dissipated decreased increase σ2. With graded cycles ε2, considerably, tensile shear When rate increased, ε1, ε3, volume εv decreased, expansion point increased. grading unloading, total exponentially. larger was, smaller variable was.