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<p>This work aims to investigate the effects of freeze–thaw (F–T) cycles on the mechanical behaviors and structure characteristics of brittle sandstone. Laboratory investigations were made to obtain the mechanical parameters and acoustic emission (AE) signals of sandstone under eight F–T cycles (0, 1, 10, 20, 30, 40, 50 and 60 times) and five confining pressures (0, 2.5, 5, 7.5 and 10&#xa0;MPa) using rock three-axis servo mechanical system and AE system. Besides, the variations in micromorphology and pore structure of the sandstone during F–T cycling were analyzed qualitatively and quantitatively using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results show that the mechanical parameters including tensile strength, triaxial compressive strength, elastic modulus, cohesion and internal friction angle decreased with increasing F–T cycles. The confining pressure and the number of freeze–thaw cycles jointly determined the failure mode of the sandstone. As the confining pressure increased, the specimens changed from splitting failure to shear failure, while the frequent F–T cycles resulted in more severe fracture of the specimens. AE data corroborates that the F–T cycles augment the activity level of AE signals from sandstone, with damage precursors evidenced by extend duration of active AE signals and reduce quiescent intervals preceding failure. SEM images show that F–T cycles precipitate a morphological evolution in sandstone’s internal structure, transitioning from a dense to a honeycomb-like configuration; the interparticle adhesion reduced during the microstructural transition, manifesting in instances of particle detachment and erosion. Results from MIP tests reveal a progressive transformation of micropores and mesopores into mesopores and macropores, respectively, as the number of F–T cycles increases. Finally, this study proposed a conceptual model to clarify the damaging mechanisms of F–T cycles on rock materials, and established an empirical equation to forecast the triaxial compressive strength of sandstone under various F–T cycles.</p>

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Multiscale Deterioration of Physical and Triaxial Mechanical Behaviors of Fine-Grained Sandstone Under Cyclic Freezing–Thawing: Experimental Observation and Microstructural Interpretation

  • 期刊论文

  • 发表日期：

    2025年6月20日

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  • Ke-Sheng Li,
  • Long-Xiao Chen,
  • Sheng-Qi Yang,
  • Gui-Lei Song,
  • Chuan-Xiao Liu

摘要

This work aims to investigate the effects of freeze–thaw (F–T) cycles on the mechanical behaviors and structure characteristics of brittle sandstone. Laboratory investigations were made to obtain the mechanical parameters and acoustic emission (AE) signals of sandstone under eight F–T cycles (0, 1, 10, 20, 30, 40, 50 and 60 times) and five confining pressures (0, 2.5, 5, 7.5 and 10 MPa) using rock three-axis servo mechanical system and AE system. Besides, the variations in micromorphology and pore structure of the sandstone during F–T cycling were analyzed qualitatively and quantitatively using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The results show that the mechanical parameters including tensile strength, triaxial compressive strength, elastic modulus, cohesion and internal friction angle decreased with increasing F–T cycles. The confining pressure and the number of freeze–thaw cycles jointly determined the failure mode of the sandstone. As the confining pressure increased, the specimens changed from splitting failure to shear failure, while the frequent F–T cycles resulted in more severe fracture of the specimens. AE data corroborates that the F–T cycles augment the activity level of AE signals from sandstone, with damage precursors evidenced by extend duration of active AE signals and reduce quiescent intervals preceding failure. SEM images show that F–T cycles precipitate a morphological evolution in sandstone’s internal structure, transitioning from a dense to a honeycomb-like configuration; the interparticle adhesion reduced during the microstructural transition, manifesting in instances of particle detachment and erosion. Results from MIP tests reveal a progressive transformation of micropores and mesopores into mesopores and macropores, respectively, as the number of F–T cycles increases. Finally, this study proposed a conceptual model to clarify the damaging mechanisms of F–T cycles on rock materials, and established an empirical equation to forecast the triaxial compressive strength of sandstone under various F–T cycles.