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<p>Expansive mudstone is a type of mudstone that is rich in highly hydrophilic clay minerals, and it swells upon contact with water. When shafts are constructed with artificial ground freezing (AGF) in water-rich expansive soft rock strata, expansive rock masses are prone to damage and degradation during freezing. This phenomenon results in frozen wall deformation and shaft lining cracking. To elucidate the failure and instability mechanisms of frozen rock walls in such areas, the mechanical properties of frozen expansive soft rock must be studied under triaxial stress conditions. Triaxial compression tests were conducted on expansive mudstone derived from the Chagannor mining area under four different moisture contents (15%, 20%, 25%, and 30%), temperatures (‒5 ℃, ‒10 ℃, ‒15 ℃, and ‒20 ℃), and confining pressures (0 MPa, 2.5 MPa, 5 MPa, and 7.5 MPa). The strength and deformation characteristics of freezing expansive mudstone under these triaxial stress conditions were investigated. The results indicated that without confining pressure, the peak strength first increased but then decreased with increasing moisture content, with the greatest strength observed at the 20% moisture content. With increasing confining pressure, the peak strength decreased as the moisture content increased, with the greatest strength observed at the 15% moisture content. The failure mode transitioned from brittle failure to plastic failure with increasing moisture content. The confining pressure suppressed crack propagation and improved the plastic characteristics of the mudstone. A lower temperature strengthened the particle bonding effect by increasing the ice content. Through X-ray diffraction (XRD) analysis and environmental scanning electron microscopy (ESEM) technology, the relationships among the mineral composition, microstructure, and macroscopic mechanical properties of mudstone were analyzed. The multiscale mechanism of the strength degradation and damage evolution trends of expansive mudstone in a freezing environment was revealed. A damage constitutive model for expansive mudstone considering residual strength was established, and the validity and effectiveness of the model were verified. This study provides a reference for the research and engineering practice related to the mechanical behaviors of expansive mudstone in cold regions and artificial freezing projects.</p>

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Mechanical Properties and Damage Constitutive Modeling of Frozen Expansive Mudstone

  • 期刊论文

  • 发表日期：

    2026年3月24日

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  • Yao Bai,
  • Jiaxu Yan,
  • Yan Luo,
  • Zhibo Xu,
  • Haoyu Dou,
  • Renliang Shan

摘要

Expansive mudstone is a type of mudstone that is rich in highly hydrophilic clay minerals, and it swells upon contact with water. When shafts are constructed with artificial ground freezing (AGF) in water-rich expansive soft rock strata, expansive rock masses are prone to damage and degradation during freezing. This phenomenon results in frozen wall deformation and shaft lining cracking. To elucidate the failure and instability mechanisms of frozen rock walls in such areas, the mechanical properties of frozen expansive soft rock must be studied under triaxial stress conditions. Triaxial compression tests were conducted on expansive mudstone derived from the Chagannor mining area under four different moisture contents (15%, 20%, 25%, and 30%), temperatures (‒5 ℃, ‒10 ℃, ‒15 ℃, and ‒20 ℃), and confining pressures (0 MPa, 2.5 MPa, 5 MPa, and 7.5 MPa). The strength and deformation characteristics of freezing expansive mudstone under these triaxial stress conditions were investigated. The results indicated that without confining pressure, the peak strength first increased but then decreased with increasing moisture content, with the greatest strength observed at the 20% moisture content. With increasing confining pressure, the peak strength decreased as the moisture content increased, with the greatest strength observed at the 15% moisture content. The failure mode transitioned from brittle failure to plastic failure with increasing moisture content. The confining pressure suppressed crack propagation and improved the plastic characteristics of the mudstone. A lower temperature strengthened the particle bonding effect by increasing the ice content. Through X-ray diffraction (XRD) analysis and environmental scanning electron microscopy (ESEM) technology, the relationships among the mineral composition, microstructure, and macroscopic mechanical properties of mudstone were analyzed. The multiscale mechanism of the strength degradation and damage evolution trends of expansive mudstone in a freezing environment was revealed. A damage constitutive model for expansive mudstone considering residual strength was established, and the validity and effectiveness of the model were verified. This study provides a reference for the research and engineering practice related to the mechanical behaviors of expansive mudstone in cold regions and artificial freezing projects.