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<p>Alpine grasslands in the seasonally frozen source region of the Yellow River experience severe sandification, intensified by freeze‒thaw (FT) cycles. In this study, the efficacy of two organic stabilizers, polyacrylamide (PAM) and modified polyvinyl alcohol (SH), in reinforcing local sandy soil was investigated. Through laboratory experiments, including direct shear tests, unconfined compressive strength (UCS) tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR), the mechanical properties and microstructural evolution of the stabilized soil in terms of different additive dosages and numbers of FT cycles were evaluated. Both stabilizers significantly increased the cohesion and UCS of the soil before FT cycling. After ten cycles, compared with PAM, SH performed markedly better, exhibiting lower cohesion loss and a unique, substantial increase in UCS. Microstructural analysis indicated that although both stabilizers initially reinforced the soil through encapsulation, cementation, and entanglement, they subsequently experienced macroscopic degradation due to adverse pore structure evolution, particularly an increase in total and macroporosity that occurred primarily during the first two cycles. In contrast, SH developed a denser and more robust network under FT cycling, which presumably accounted for its distinct increase in UCS. Considering both mechanical performance and cost, a 3% dosage of SH was recommended for sand fixation projects in the Yellow River source region.</p>

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Mechanical behaviour and microstructural evolution of organic material-stabilized sandy soil under freeze‒thaw cycles

  • 期刊论文

  • 发表日期：

    2026年3月7日

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  • Bentao Ma,
  • Yingbin Guo,
  • Peiyuan Zhan,
  • Chunye Ying,
  • Hanbo Gao

摘要

Alpine grasslands in the seasonally frozen source region of the Yellow River experience severe sandification, intensified by freeze‒thaw (FT) cycles. In this study, the efficacy of two organic stabilizers, polyacrylamide (PAM) and modified polyvinyl alcohol (SH), in reinforcing local sandy soil was investigated. Through laboratory experiments, including direct shear tests, unconfined compressive strength (UCS) tests, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR), the mechanical properties and microstructural evolution of the stabilized soil in terms of different additive dosages and numbers of FT cycles were evaluated. Both stabilizers significantly increased the cohesion and UCS of the soil before FT cycling. After ten cycles, compared with PAM, SH performed markedly better, exhibiting lower cohesion loss and a unique, substantial increase in UCS. Microstructural analysis indicated that although both stabilizers initially reinforced the soil through encapsulation, cementation, and entanglement, they subsequently experienced macroscopic degradation due to adverse pore structure evolution, particularly an increase in total and macroporosity that occurred primarily during the first two cycles. In contrast, SH developed a denser and more robust network under FT cycling, which presumably accounted for its distinct increase in UCS. Considering both mechanical performance and cost, a 3% dosage of SH was recommended for sand fixation projects in the Yellow River source region.