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<p>To address the research gap in fatigue damage characteristics and theoretical modeling of transversely isotropic soft–hard interbedded rocks, a comprehensive investigation is conducted through multi-stage triaxial cyclic fatigue tests on composite rocks. Key experimental variables including bedding inclination angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°), confining pressures (0, 12, 24, and 36&#xa0;MPa), amplitude increments (10, 20, 30, and 40&#xa0;MPa), and number of cycles (10, 30, 60, and 100) are designed. The results demonstrate that: the fatigue life and peak strength of the composite rock decrease and then increase with the increasing bedding angles, exhibit continuous enhancement under elevated confining pressure, undergo significant degradation with cycle accumulation, and display an initial rise followed by decline as amplitude increment grows. Compared to failure modes under static loading, cyclic loading induces more complex failure modes in composite rocks, manifested by progressively increasing crack density and fragmentation. The CT reconstruction results verify the above phenomena. The cohesion and internal friction angle of transversely isotropic rocks are corrected based on the M–C criterion and are introduced into the D–P criterion. Modified strength criterion can well predict the strength characteristics of composite rock formations under different confining pressures with different bedding angles. Ultimately, a dynamic fractional-order damage fatigue mechanics model is established by combining the disturbance damage and the fractional mechanics elements. The model is capable of realizing the deformation behavior of composite rock under fatigue loading.</p>

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Experimental and Theoretical Investigations of Fatigue Mechanical Behavior of Transversely Isotropic Composite Rocks

  • 期刊论文

  • 发表日期：

    2025年10月14日

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  • Yu Song,
  • Sheng-Qi Yang,
  • Xiang-Xi Meng,
  • Ke-Sheng Li,
  • Yan-Hua Huang,
  • Li-Feng Fan

摘要

To address the research gap in fatigue damage characteristics and theoretical modeling of transversely isotropic soft–hard interbedded rocks, a comprehensive investigation is conducted through multi-stage triaxial cyclic fatigue tests on composite rocks. Key experimental variables including bedding inclination angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°), confining pressures (0, 12, 24, and 36 MPa), amplitude increments (10, 20, 30, and 40 MPa), and number of cycles (10, 30, 60, and 100) are designed. The results demonstrate that: the fatigue life and peak strength of the composite rock decrease and then increase with the increasing bedding angles, exhibit continuous enhancement under elevated confining pressure, undergo significant degradation with cycle accumulation, and display an initial rise followed by decline as amplitude increment grows. Compared to failure modes under static loading, cyclic loading induces more complex failure modes in composite rocks, manifested by progressively increasing crack density and fragmentation. The CT reconstruction results verify the above phenomena. The cohesion and internal friction angle of transversely isotropic rocks are corrected based on the M–C criterion and are introduced into the D–P criterion. Modified strength criterion can well predict the strength characteristics of composite rock formations under different confining pressures with different bedding angles. Ultimately, a dynamic fractional-order damage fatigue mechanics model is established by combining the disturbance damage and the fractional mechanics elements. The model is capable of realizing the deformation behavior of composite rock under fatigue loading.