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<p>Progressive fracture propagation, under coupled cyclic stress-moisture conditions, critically governs stability degradation of rock masses in underground engineering. This study has investigated the mechanical and energy responses of rocks under triaxial cyclic stress. The results demonstrated that with cycle numbers growing, the hysteresis loops exhibited an evolution pattern from dense to sparse. Under lower confining pressure (5&#xa0;MPa), the hysteresis loops approximated a willow leaf shape, while at higher confining pressure (20&#xa0;MPa), it transitioned to a shuttle-shaped morphology. The disparity between rocks loading/unloading deformation modulus progressively amplified with its increasing confining pressure. Notably, the axial residual deformation attained a significant magnitude during first cycle but underwent marked attenuation in subsequent cycles. This phenomenon highlighted the critical role of confining pressure in modulating rock’s hysteretic behavior and irreversible deformation. The total energy, for both saturated and dry red sandstone, demonstrated exponential growth in later cycle stages, while the elastic energy maintained a rapid amplification mode throughout entire cycle loading–unloading process. Its dissipative energy also initiated accelerated growth during its later cycles, with its growth curve approximating a steep linear pattern. Moreover, the primary cracks of saturated red sandstone generally exhibited relatively large angles with horizontal direction, and it displayed a smaller proportion of tensile cracks than dry specimens. This contrast highlighted the significant influence of saturation on fracture mechanism and energy partitioning of rocks under cyclic stress, where water–rock interactions fundamentally modified cracks propagation mode and energy redistribution pathway.</p>

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Experimental study on mechanical behavior and energy response characteristic of red sandstone under triaxial cyclic loading and unloading

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年12月29日

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  • Bin Sui,
  • Ansen Gao,
  • Chengzhi Qi,
  • Chunlai Wang,
  • Zhen Wei,
  • Genshui Wu

摘要

Progressive fracture propagation, under coupled cyclic stress-moisture conditions, critically governs stability degradation of rock masses in underground engineering. This study has investigated the mechanical and energy responses of rocks under triaxial cyclic stress. The results demonstrated that with cycle numbers growing, the hysteresis loops exhibited an evolution pattern from dense to sparse. Under lower confining pressure (5 MPa), the hysteresis loops approximated a willow leaf shape, while at higher confining pressure (20 MPa), it transitioned to a shuttle-shaped morphology. The disparity between rocks loading/unloading deformation modulus progressively amplified with its increasing confining pressure. Notably, the axial residual deformation attained a significant magnitude during first cycle but underwent marked attenuation in subsequent cycles. This phenomenon highlighted the critical role of confining pressure in modulating rock’s hysteretic behavior and irreversible deformation. The total energy, for both saturated and dry red sandstone, demonstrated exponential growth in later cycle stages, while the elastic energy maintained a rapid amplification mode throughout entire cycle loading–unloading process. Its dissipative energy also initiated accelerated growth during its later cycles, with its growth curve approximating a steep linear pattern. Moreover, the primary cracks of saturated red sandstone generally exhibited relatively large angles with horizontal direction, and it displayed a smaller proportion of tensile cracks than dry specimens. This contrast highlighted the significant influence of saturation on fracture mechanism and energy partitioning of rocks under cyclic stress, where water–rock interactions fundamentally modified cracks propagation mode and energy redistribution pathway.