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<p>Freeze-thaw (F-T) action can induce strength reduction and instability of rock mass in cold regions. To clarify the differential degradation of mode I fracture toughness (<i>K</i><sub>IC</sub>) and mode II fracture toughness (<i>K</i><sub>IIC</sub>) affected by F-T cycles, semi-circular bend (SCB) fracture test, NMR analysis, and P-wave velocity (<i>V</i><sub>p</sub>) measurement were employed in this study. The experimental results show that <i>K</i><sub>IC</sub> and <i>K</i><sub>IIC</sub> decrease significantly with increasing F-T cycles. After 60 F-T cycles, the <i>K</i><sub>IC</sub> and <i>K</i><sub>IIC</sub> decrease by 80.32% and 65.25%, respectively. NMR analysis reveals that this degradation is primarily driven by the expansion and coalescence of micropores. A prediction model of fracture toughness is established using the F-T damage variable defined by <i>V</i><sub>p</sub>. A novel finding is that the F-T degradation of <i>K</i><sub>IIC</sub> can be well predicted while <i>K</i><sub>IC</sub> is overestimated using this model, because the growth of micropores is more conducive to the development of mode I cracks. In addition, statistical analysis validates that the F-T damage variable based on <i>V</i><sub>p</sub> is more suitable for directly predicting the strength of shear failure modes such as uniaxial compressive strength (UCS) and peak shear strength (<i>τ</i><sub>p</sub>). This study provides a better understanding of the differential influence of F-T damage on shear and tensile failure strength, and reference for the stability evaluation of rock mass in cold regions.</p>

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Study on the Correlation Mechanism Between Mode I/II Fracture Toughness Evolution and Freeze-Thaw Damage in Red Sandstone Under Freeze-Thaw Cycles

  • 期刊论文

  • 发表日期：

    2026年2月18日

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  • Jiawei Zhai,
  • Shibing Huang,
  • Luobin Zheng,
  • Zexin Lu

摘要

Freeze-thaw (F-T) action can induce strength reduction and instability of rock mass in cold regions. To clarify the differential degradation of mode I fracture toughness (KIC) and mode II fracture toughness (KIIC) affected by F-T cycles, semi-circular bend (SCB) fracture test, NMR analysis, and P-wave velocity (Vp) measurement were employed in this study. The experimental results show that KIC and KIIC decrease significantly with increasing F-T cycles. After 60 F-T cycles, the KIC and KIIC decrease by 80.32% and 65.25%, respectively. NMR analysis reveals that this degradation is primarily driven by the expansion and coalescence of micropores. A prediction model of fracture toughness is established using the F-T damage variable defined by Vp. A novel finding is that the F-T degradation of KIIC can be well predicted while KIC is overestimated using this model, because the growth of micropores is more conducive to the development of mode I cracks. In addition, statistical analysis validates that the F-T damage variable based on Vp is more suitable for directly predicting the strength of shear failure modes such as uniaxial compressive strength (UCS) and peak shear strength (τp). This study provides a better understanding of the differential influence of F-T damage on shear and tensile failure strength, and reference for the stability evaluation of rock mass in cold regions.