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<p>The freeze–thaw (FT) damage of rocks is a principal cause of frost damage in engineering in cold regions. Present studies on the FT damage of rocks are mainly based on uniform FT experiments. However, in cold region engineering, the situations where rocks suffer unidirectional FT action exist extensively. Currently, the understanding of the mechanical damage evolution and its mechanisms of rocks under unidirectional FT action is insufficient. Therefore, in this study, based on the unidirectional FT cycling tests and uniaxial compression tests, the compressive strength and stress–strain curves of sandstone parallel and perpendicular to the freeze–thaw direction (FTD) after unidirectional FT action are compared and analyzed to investigate the damage evolution of rock mechanical properties under unidirectional FT action. Moreover, the evolution mechanism of the mechanical properties of rocks under unidirectional FT conditions is revealed, based on the distribution of micro-fractures of sandstone, the failure modes, and the P-wave velocities parallel and perpendicular to FTD after unidirectional FT action. Experimental results reveal that under unidirectional FT action, both red sandstone and green sandstone exhibit a greater compressive strength parallel to FTD than that perpendicular to FTD. The peak strain parallel to FTD is also greater than that perpendicular to FTD. The sandstone evolves from the initial isotropic property to a transversely isotropic property. After suffering unidirectional FT cycling, the cementation degree of sandstone particles declines, with the formation of long strip-shaped micro-fractures, and the orientation direction of the micro-fractures is approximately perpendicular to FTD. The directional development of micro-fractures in rocks under unidirectional FT action results in a higher wave velocity of sandstone perpendicular to FTD than that parallel to FTD. The compressive failure mode parallel to FTD is an X-type compressive-shear failure mode, while the compressive failure mode perpendicular to FTD is a splitting failure mode with the failure surface along the loading direction.</p>

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Experimental Study on Evolution of Transversely Isotropic Mechanical Characteristics of Rocks Under Unidirectional Freeze–Thaw Action

  • 期刊论文

  • 发表日期：

    2025年11月4日

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  • Zhitao Lv,
  • Yang Liu,
  • Yi Cai,
  • Caichu Xia,
  • Weiping Liu

摘要

The freeze–thaw (FT) damage of rocks is a principal cause of frost damage in engineering in cold regions. Present studies on the FT damage of rocks are mainly based on uniform FT experiments. However, in cold region engineering, the situations where rocks suffer unidirectional FT action exist extensively. Currently, the understanding of the mechanical damage evolution and its mechanisms of rocks under unidirectional FT action is insufficient. Therefore, in this study, based on the unidirectional FT cycling tests and uniaxial compression tests, the compressive strength and stress–strain curves of sandstone parallel and perpendicular to the freeze–thaw direction (FTD) after unidirectional FT action are compared and analyzed to investigate the damage evolution of rock mechanical properties under unidirectional FT action. Moreover, the evolution mechanism of the mechanical properties of rocks under unidirectional FT conditions is revealed, based on the distribution of micro-fractures of sandstone, the failure modes, and the P-wave velocities parallel and perpendicular to FTD after unidirectional FT action. Experimental results reveal that under unidirectional FT action, both red sandstone and green sandstone exhibit a greater compressive strength parallel to FTD than that perpendicular to FTD. The peak strain parallel to FTD is also greater than that perpendicular to FTD. The sandstone evolves from the initial isotropic property to a transversely isotropic property. After suffering unidirectional FT cycling, the cementation degree of sandstone particles declines, with the formation of long strip-shaped micro-fractures, and the orientation direction of the micro-fractures is approximately perpendicular to FTD. The directional development of micro-fractures in rocks under unidirectional FT action results in a higher wave velocity of sandstone perpendicular to FTD than that parallel to FTD. The compressive failure mode parallel to FTD is an X-type compressive-shear failure mode, while the compressive failure mode perpendicular to FTD is a splitting failure mode with the failure surface along the loading direction.