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<p>By combining the pressure plate, saturated salt solution–vapour equilibrium, and WP4C instrument methods, a soil-water characteristic curve (SWCC) for expansive soil at all suctions during drying‒wetting cycles was obtained, and expansive soil hysteresis and volume changes were analysed. Microstructural scanning electron microscopy (SEM) and pore size distribution (PSD) tests were conducted on samples along the wetting path to study microstructural evolution of expansive soil in canal embankments at all suctions. The expansive SWCC at all suctions exhibits hysteresis due to the nonuniform pore distribution, contact angle hysteresis, and trapped air. The energy required for the suction balance differs between the wetting and drying paths. The pore volume of saturated expansive soil is the largest, and the volume decreases with increasing matric suction. Same-void-ratio expansive soils have different degrees of saturation, indicating a significant coupling effect between saturation and void ratio (specific volume) with changes in matric suction. Expansive soils have dual-pore structures with inter/ inter- and intra-aggregate pores. The boundary between the inter/intra-aggregate pores is 0.2&#xa0;μm. The intra-aggregate pore volume distribution is consistent at all suctions. During initial wetting, the dominant pore diameter decreases and the macropores close. During intermediate wetting, the pore distribution remains relatively unchanged. During final wetting, the pore distribution changes and aggregate expansion deformation and soil expansion occur. Due to differences in the liquid phase properties of macro- and micropores, the pore structure and distribution of expansive soil undergo significant changes with variations in hydromechanical properties.</p>

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Hydro-mechanical coupling and microstructural evolution mechanism of expansive soil under full suction range

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年2月11日

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  • Dubo Wang,
  • Mengzi Li,
  • Zhuoran Wang

摘要

By combining the pressure plate, saturated salt solution–vapour equilibrium, and WP4C instrument methods, a soil-water characteristic curve (SWCC) for expansive soil at all suctions during drying‒wetting cycles was obtained, and expansive soil hysteresis and volume changes were analysed. Microstructural scanning electron microscopy (SEM) and pore size distribution (PSD) tests were conducted on samples along the wetting path to study microstructural evolution of expansive soil in canal embankments at all suctions. The expansive SWCC at all suctions exhibits hysteresis due to the nonuniform pore distribution, contact angle hysteresis, and trapped air. The energy required for the suction balance differs between the wetting and drying paths. The pore volume of saturated expansive soil is the largest, and the volume decreases with increasing matric suction. Same-void-ratio expansive soils have different degrees of saturation, indicating a significant coupling effect between saturation and void ratio (specific volume) with changes in matric suction. Expansive soils have dual-pore structures with inter/ inter- and intra-aggregate pores. The boundary between the inter/intra-aggregate pores is 0.2 μm. The intra-aggregate pore volume distribution is consistent at all suctions. During initial wetting, the dominant pore diameter decreases and the macropores close. During intermediate wetting, the pore distribution remains relatively unchanged. During final wetting, the pore distribution changes and aggregate expansion deformation and soil expansion occur. Due to differences in the liquid phase properties of macro- and micropores, the pore structure and distribution of expansive soil undergo significant changes with variations in hydromechanical properties.