研究非饱和土的水力特性对分析工程建设活动中黄土的渗流和变形问题具有重要意义。以西安市南郊黄土为研究对象,采用滤纸法和饱和盐溶液法测得3种干密度下的黄土增减湿土-水特征曲线,并通过Childs & Collis-George模型预测试验黄土的非饱和渗透系数,探究干密度和增减湿对非饱和渗透特性的影响。结果表明:经历增减湿的土样的非饱和渗透系数曲线应结合土样的含水状态和对应的土-水特征曲线来预测;土体非饱和渗透系数随体积含水率的增大而增大,随基质吸力的增大而减小,在0~5 MPa范围快速衰减4~5个数量级;受瓶颈效应和减湿收缩的影响,土体增湿阶段渗透系数变化幅度小于减湿阶段的变化幅度;渗透系数随干密度增大而减小,干密度从1.719 g/cm³增大到1.834 g/cm³,渗透系数减小2个数量级;压实黄土在增减湿阶段的非饱和渗透系数最大可相差3~4倍。

The study of hydraulic characteristics in unsaturated soils is crucial for analyzing seepage and deformation of loess during engineering activities. This research focuses on loess from the southern suburbs of Xi’an City. The filter paper method and saturated salt solution method were employed to measure soil-water characteristic curves under three dry density conditions with varying degrees of wetness. The Childs & Collis-George model was used to predict unsaturated permeability coefficient, examining the impacts of dry density and wetting/drying cycles on these characteristics. Results indicate that unsaturated permeability coefficient increased with volumetric moisture content and decreased with matric suction, dropping significantly by 4-5 orders of magnitude within the 0-5 MPa range. Due to bottleneck effects and moisture-reduction-induced shrinkage, the variation in permeability coefficient during wetting stages was smaller compared to drying stages. Furthermore, with dry density increasing from 1.719 g/cm³ to 1.834 g/cm³, permeability coefficient decreased by two orders of magnitude. The unsaturated permeability coefficient of compacted loess varied by a factor of up to 3-4 between wetting and drying phases.