Effects of pre-existing single crack angle on mechanical behaviors and energy storage characteristics of red sandstone under uniaxial compression

To investigate the effects of the pre-existing single crack angle on the mechanical behaviors and energy storage characteristics of red sandstone, a series of uniaxial compression and single-cyclic loading-unloading uniaxial compression tests were conducted on red sandstone specimens with five crack angles. The relationships among the crack angle and the mechanical properties, failure modes, and energy storage characteristics of red sandstone were analyzed using the acoustic emission (AE), stress-strain curve and curvilinear integral. The results indicate that the peak compressive strength, peak strain, and elastic modulus of specimens increase with the crack angle increasing, and the specimens with five different angles all present anti-N-type shear failure. Throughout the loading process, the total input energy density, elastic strain energy density, and dissipated energy density of the red sandstone at five different crack angles exhibit significant quadratic growth in response to the actual unloading stress. Importantly, the elastic strain energy density and dissipated energy density of red sandstone with different crack angles all show highly linear relationships with the total input energy density, and the linear energy storage and dissipation laws of pre-cracked rocks are obtained. Based on the linear energy storage law, the energy densities at peak strength of red sandstone with different crack angles are determined quantitatively. In addition, the linear energy dissipation law is applied to the expression of rock damage, and the damage constitutive equations of uniaxial compression specimens with different crack angles are obtained. Finally, the effects of crack geometric parameters on the energy storage and dissipation characteristics were discussed.

Automated summary

The study investigated the effects of pre-existing single crack angles on the mechanical behaviors and energy storage characteristics of red sandstone. Results showed that peak compressive strength, peak strain, and elastic modulus of specimens increase with crack angle, and specimens exhibited anti-N-type shear failure. Energy densities at peak strength were quantitatively determined based on linear energy storage law, and damage constitutive equations were obtained for specimens with different crack angles.