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<p>Understanding the strength and deformation behavior of recompacted loess is essential for the stability assessment of man-made geotechnical structures in loess regions. While numerous studies have examined the macroscopic mechanical properties of unsaturated recompacted loess, the underlying particle-scale micromechanical deformation mechanisms remain inadequately explored. In this study, a series of drained triaxial tests were conducted on unsaturated recompacted loess under varying matric suctions and mean net stresses to investigate their effects on strength and deformation behavior. The experimental results indicate that higher matric suction increases deviatoric stress due to suction-induced apparent cohesion, whose influence weakens with increasing mean net stress. Moreover, all specimens exhibit continuous volumetric contraction during shearing, consistent with the strain-hardening behavior observed in the stress–strain curves. To interpret these observations from a micromechanical perspective, the original Hill contact model within the discrete element method (DEM) framework was modified by incorporating suction-dependent micromechanical parameters. The modified model was calibrated and validated against laboratory data, showing good agreement in reproducing both stress–strain and volumetric deformation behaviors. Further micromechanical analysis reveals that suction enhances capillary bonding at low net stress, but its influence diminishes as the mean net stress increases. Specifically, at low net stress, higher suction results in a greater proportion of tensile (i.e., capillary) contacts and slightly reduced particle displacements, indicating stronger interparticle bonding. As the mean net stress increases, particle displacements become slightly larger and contact stability is primarily governed by vertical contact forces rather than suction effects. These micromechanical insights are consistent with the experimental observations, thereby establishing a clear link between particle-scale interactions and macroscopic mechanical responses.</p> Graphical Abstract <p></p>

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Strength and deformation of unsaturated recompacted loess: a multi-scale study via experiments and DEM simulations

  • 期刊论文

  • 发表日期：

    2026年1月13日

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  • Yingpeng Fu,
  • Linfei Wu,
  • Hongjian Liao,
  • Yao Li,
  • Longlong Lv

摘要

Understanding the strength and deformation behavior of recompacted loess is essential for the stability assessment of man-made geotechnical structures in loess regions. While numerous studies have examined the macroscopic mechanical properties of unsaturated recompacted loess, the underlying particle-scale micromechanical deformation mechanisms remain inadequately explored. In this study, a series of drained triaxial tests were conducted on unsaturated recompacted loess under varying matric suctions and mean net stresses to investigate their effects on strength and deformation behavior. The experimental results indicate that higher matric suction increases deviatoric stress due to suction-induced apparent cohesion, whose influence weakens with increasing mean net stress. Moreover, all specimens exhibit continuous volumetric contraction during shearing, consistent with the strain-hardening behavior observed in the stress–strain curves. To interpret these observations from a micromechanical perspective, the original Hill contact model within the discrete element method (DEM) framework was modified by incorporating suction-dependent micromechanical parameters. The modified model was calibrated and validated against laboratory data, showing good agreement in reproducing both stress–strain and volumetric deformation behaviors. Further micromechanical analysis reveals that suction enhances capillary bonding at low net stress, but its influence diminishes as the mean net stress increases. Specifically, at low net stress, higher suction results in a greater proportion of tensile (i.e., capillary) contacts and slightly reduced particle displacements, indicating stronger interparticle bonding. As the mean net stress increases, particle displacements become slightly larger and contact stability is primarily governed by vertical contact forces rather than suction effects. These micromechanical insights are consistent with the experimental observations, thereby establishing a clear link between particle-scale interactions and macroscopic mechanical responses.

Graphical Abstract