干湿循环作用下黄土水力特性及其裂隙演化规律

    Hydraulic characteristics and fracture evolution of loess under wetting-drying cycles

    • 摘要: 黄土高原是中国地质灾害最为高发的地区之一,尤其是近年来,区域内极端暴雨和长期干旱事件频发,导致黄土塬边地下水位升降带的黄土长期遭受反复干湿循环作用,加剧了黄土滑坡的风险。本文对泾阳南塬原状黄土进行了不同干湿循环次数下土-水特征曲线测试和饱和渗透试验以及裂隙演化分析。结果表明:①干湿循环作用驱动土-水特征曲线整体向左偏移,土体持水能力显著减弱,饱和渗透系数呈指数函数型增长规律。②V-G模型可有效描述原状干湿循环作用后黄土的土-水特征曲线,基于拟合参数的变化特征构建了泾阳南塬原状黄土的土-水特征曲线预测模型。③干湿循环通过驱动裂隙演化过程,动态重塑了土-水特征曲线,进而改变了黄土的渗流特性;将黄土干湿循环作用下的裂隙演化过程分成了形成、发展和愈合3个阶段。④揭示了黄土水力特性与裂隙演化之间的规律:前期干湿循环对黄土水力特性和细观结构的劣化影响显著,通过干湿循环的正反馈作用进一步促进了黄土裂隙的形成和发展;多次干湿循环作用后黄土裂隙达到愈合临界点,细观结构重组与胶结物填充促使裂隙愈合,最终土体裂隙趋于稳定。

       

      Abstract: The Loess Plateau is one of the most geologically hazardous regions in China. In recent years, frequent extreme rainstorms and prolonged droughts in the area have caused repeated dry-wet cycles in the loess within the groundwater fluctuation zone at the edges of loess tablelands, exacerbating landslide risks. This study conducts soil-water characteristic curve (SWCC) tests, saturated permeability tests, and crack evolution analyses on intact loess from the Jingyang South Tableland under varying dry-wet cycles. The results indicate that: (1) Dry-wet cycles shift the SWCC leftward, significantly reducing soil water retention capacity, while the saturated permeability coefficient follows an exponential growth pattern. (2) The Van Genuchten (VG) model effectively describes the SWCC of intact loess after dry-wet cycles. Based on variations in fitting parameters, a predictive SWCC model is established. (3) Dry-wet cycles dynamically reshape the SWCC by driving crack evolution, thereby altering loess seepage characteristics. The crack evolution process under dry-wet cycles is divided into three stages: formation, development, and healing. (4) The mechanism linking loess hydraulic properties and crack evolution is revealed: initial dry-wet cycles significantly degrade hydraulic properties and meso-structure, further promoting crack initiation and propagation through positive feedback. After multiple cycles, cracks reach a healing threshold, with meso-structural reorganization and cementation filling leading to crack stabilization.

       

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