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<p>The mechanical properties degradation of rocks at low temperatures can cause serious geological disasters in cold regions. These are important for the stability and safety of rock engineering in cold regions and artificial freezing engineering. In this research, the changes in the uniaxial compressive strength (UCS), direct shear strength (DSS), cohesion, internal friction angle (IFA), and Brazilian tensile strength (BTS) of sandstones during thawing were comprehensively investigated. The pore size distribution (PSD) and variation in unfrozen water content (UWC) during thawing were monitored using nuclear magnetic resonance (NMR). This indicates that the thawing of pore ice is the dominant reason for the reduction in the mechanical strengths of porous sandstone, and sandstone with higher porosity exhibits greater strength loss during thawing. A natural exponential function was established to quantify the relationship between the strength parameters and UWC after normalization, which can be used to estimate the strength parameters at any temperature. As the normalized UWC increased from 0 to 20%, almost all the strength parameters decreased by 80%; therefore, this implies that a slight thawing of pore ice will cause a significant reduction in the strength of low-temperature rocks. In addition, the brittleness indexes calculated by UCS and BTS also decreased by 95.27% and 78.26%, respectively, after complete thawing from −20&#xa0;℃. This study provides a better understanding of the mechanical strength variation in sandstone during thawing and its quantification relationship with the UWC.</p>

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Mechanical Strength Variation of Low-Temperature Sandstones During Thawing Process by Considering the Effect of Unfrozen Water Content

  • 期刊论文

  • 发表日期：

    2025年6月9日

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  • Fei Liu,
  • Shibing Huang,
  • Yongshui Kang,
  • Luobin Zheng,
  • Gang Liu,
  • Kaunda Musonda

摘要

The mechanical properties degradation of rocks at low temperatures can cause serious geological disasters in cold regions. These are important for the stability and safety of rock engineering in cold regions and artificial freezing engineering. In this research, the changes in the uniaxial compressive strength (UCS), direct shear strength (DSS), cohesion, internal friction angle (IFA), and Brazilian tensile strength (BTS) of sandstones during thawing were comprehensively investigated. The pore size distribution (PSD) and variation in unfrozen water content (UWC) during thawing were monitored using nuclear magnetic resonance (NMR). This indicates that the thawing of pore ice is the dominant reason for the reduction in the mechanical strengths of porous sandstone, and sandstone with higher porosity exhibits greater strength loss during thawing. A natural exponential function was established to quantify the relationship between the strength parameters and UWC after normalization, which can be used to estimate the strength parameters at any temperature. As the normalized UWC increased from 0 to 20%, almost all the strength parameters decreased by 80%; therefore, this implies that a slight thawing of pore ice will cause a significant reduction in the strength of low-temperature rocks. In addition, the brittleness indexes calculated by UCS and BTS also decreased by 95.27% and 78.26%, respectively, after complete thawing from −20 ℃. This study provides a better understanding of the mechanical strength variation in sandstone during thawing and its quantification relationship with the UWC.