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<p>Time-dependent heave deformation in red-bed soft rock (RBSR) subgrades poses a critical threat to high-speed railway safety. However, its creep mechanism remains unclear because of limited understanding of the creep properties of red-bed silty mudstone (RBSM) and the lack of suitable constitutive models. In this study, multistage loading creep tests with acoustic&#xa0;emission (AE) monitoring are conducted on RBSM under different water contents and low confining pressures. A unified nonlinear creep damage-coupled model is developed by combining statistical damage theory with fractional calculus. Experimental results show that RBSM exhibits stress-dependent nonlinear creep behavior, including viscoelastic deformation at low-stress levels, viscoelastic-viscoplastic deformation at intermediate stress levels, and trimodal deformation at high stress levels. The long-term strength remains within 64-75% of the compressive strength under different water contents and confining pressures, close to the crack&#xa0;damage stress from conventional compression tests. The steady-state creep rate is highly sensitive to deviatoric stress and water content. Failure patterns evolve from X-shaped conjugate shear cracks to single shear cracks with decreasing water content and increasing confining pressure. The proposed model captures the full-spectrum nonlinear response during both instantaneous and constant loading stages. Unlike traditional models, its parameters are stress-independent and effectively capture the coupling effects of water and confining pressure, providing a basis for analyzing creep-induced heave in RBSR subgrades.</p>

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Creep Mechanical Properties and a Unified Nonlinear Creep Damage Coupled Model of Red-Bed Silty Mudstone Under Different Water Content and Confining Pressure

  • 期刊论文

  • 发表日期：

    2026年5月13日

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  • Qiang Xie,
  • Binqi Yan,
  • Dalang Tian,
  • Bolin Chen,
  • Zhengchuan Li,
  • Qiang Xiao,
  • Yuxin Ban

摘要

Time-dependent heave deformation in red-bed soft rock (RBSR) subgrades poses a critical threat to high-speed railway safety. However, its creep mechanism remains unclear because of limited understanding of the creep properties of red-bed silty mudstone (RBSM) and the lack of suitable constitutive models. In this study, multistage loading creep tests with acoustic emission (AE) monitoring are conducted on RBSM under different water contents and low confining pressures. A unified nonlinear creep damage-coupled model is developed by combining statistical damage theory with fractional calculus. Experimental results show that RBSM exhibits stress-dependent nonlinear creep behavior, including viscoelastic deformation at low-stress levels, viscoelastic-viscoplastic deformation at intermediate stress levels, and trimodal deformation at high stress levels. The long-term strength remains within 64-75% of the compressive strength under different water contents and confining pressures, close to the crack damage stress from conventional compression tests. The steady-state creep rate is highly sensitive to deviatoric stress and water content. Failure patterns evolve from X-shaped conjugate shear cracks to single shear cracks with decreasing water content and increasing confining pressure. The proposed model captures the full-spectrum nonlinear response during both instantaneous and constant loading stages. Unlike traditional models, its parameters are stress-independent and effectively capture the coupling effects of water and confining pressure, providing a basis for analyzing creep-induced heave in RBSR subgrades.