关键词: 砂岩, 脆性破坏, Ⅱ类曲线, 环向控制速率, 耗散能

Abstract:

To investigate the influence of circumferential loading rates on the mechanical properties of sandstone, uniaxial compression tests were conducted on sandstone specimens at various circumferential control rates using an MTS rigid servo testing machine. The effects of circumferential control rate on stress-strain curves, failure modes, and energy evolution were analyzed. Results indicate that circumferential control rates have minimal impact on pre-peak deformation and peak strength, while reducing post-peak stress and strains. As circumferential control rate decreases, the post-peak axial stress-strain curves experience alternating stress decreases and increases. Post-peak volumetric strain exhibit the same trend. Although circumferential control rate does not significantly affect rock brittleness, the time required for rock failure increases sharply as the control rate decreases. Circumferential control yields predominantly shear failure, with lower total dissipated energy during pre-peak stage. As circumferential control rate decreases, dissipated energy gradually increases during post-peak stage, which weakens the post-peak failure and makes it controllable. On the contrary, under axial control mode, axial splitting is the dominant failure mode, with sharp increases in lateral strain post-peak and violent failure. These findings provide valuable insights for understanding the rock loading ratio effect and the brittle rock deformation characteristics under circumferential control conditions.

Key words: sandstone, brittle failure, class Ⅱ curve, circumferential control rate, dissipated energy