ISSN 1009-6248CN 61-1149/P 双月刊

主管单位:中国地质调查局

主办单位:中国地质调查局西安地质调查中心
中国地质学会

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    冻融循环作用下不同区域湿陷性黄土持水特性区域差异

    Regional Differences in the Water Retention Behavior of Collapsible Loess under Freeze-Thaw Cycles

    • 摘要: 黄土广泛分布于中国季节冻土区,其颗粒组成、孔隙结构及工程性质具有显著区域分带性。冻融循环作用下,黄土内部孔隙结构持续重组,进而影响其持水能力及土水特征曲线(SWCC)演化。为揭示不同区域湿陷性黄土在冻融循环作用下的持水特性差异,选取宁夏砂黄土、山西粉黄土和泾阳黏黄土3类原状黄土为研究对象,考虑不同初始含水率和冻融循环次数,采用压力膜仪测定土水特征曲线,并利用 Fredlund–Xing 模型进行拟合分析。结果表明:不同区域黄土 SWCC 均呈典型“S”形,冻融循环引起的差异主要集中在主脱饱和段和高吸力尾部;泾阳土样对冻融作用最为敏感并表现为明显的阶段性重组,宁夏土样表现出较强的含水率分化特征,山西土样整体变化较为平缓;Fredlund–Xing 模型参数abc均随冻融条件发生变化,表明冻融循环不仅改变了进气特征,而且改变了主脱饱和段斜率和高吸力区残余持水特征。区域差异不仅决定黄土初始持水能力,也影响冻融扰动下孔隙结构重组的路径。研究结果可为季节冻土区黄土工程中非饱和渗流分析、冻融劣化评价及水致灾害防控提供试验依据。

       

      Abstract: Loess is widely distributed in the seasonally frozen regions of China, and its particle composition, pore structure, and engineering properties exhibit significant regional zonation. Under freeze–thaw cycles, the internal pore structure of loess is continuously restructured, thereby affecting its water-holding capacity and the evolution of the soil-water characteristic curve (SWCC). To investigate the regional differences in the water-holding behavior of collapsible loess under freeze–thaw cycles, undisturbed sandy loess from Ningxia, silty loess from Shanxi, and clayey loess from Jingyang were selected. Considering different initial water contents and freeze–thaw cycle numbers, SWCCs were measured using a pressure plate apparatus and fitted with the Fredlund–Xing model. The results show that all SWCCs exhibit a typical S-shaped pattern, and the differences induced by freeze–thaw cycles are mainly concentrated in the main desaturation stage and the high-suction tail. Jingyang samples are the most sensitive to freeze–thaw action and show obvious staged restructuring; Ningxia samples exhibit pronounced moisture-content-dependent divergence; Shanxi samples change more gently overall. The fitted parameters a, b, and c all vary with freeze–thaw conditions, indicating that freeze–thaw cycles not only alter the air-entry-related feature, but also change the slope of the main desaturation section and the residual water-retention behavior in the high-suction range. Regional differences therefore control not only the initial water-holding capacity of loess, but also the restructuring path of its pore system under freeze–thaw disturbance. These findings provide an experimental basis for unsaturated seepage analysis, freeze–thaw degradation assessment, and water-induced hazard prevention in loess engineering in seasonally frozen regions.

       

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