晚更新世黄土渗透性的各向异性及其机制研究

非饱和黄土的渗透性是非饱和黄土性质的重要组成部分。研究黄土不同方向的渗透性对确定其湿陷范围和由于水的渗透引起的黄土滑坡具有很重要的理论意义。研究了黄土渗透性的各向异性特征及其机制。以具有明显各向异性的西安Q3原状黄土为研究对象，用TEN型张力计测量了黄土试样不同方向的、不同含水率下的吸力；用变水头渗透试验测量了黄土竖直和水平方向的饱和渗透系数。结果表明，当体积含水率在23%～41%时，张力计沿不同方向插入土样所测吸力相差不大；竖直方向的饱和渗透系数是水平方向的4.02倍。在吸力测量的基础上，根据土-水特征曲线，确定了竖直和水平方向的非饱和黄土的渗透系数。得出在黄土不同方向，随着吸力的增大或减小，渗透系数减小或增大；竖直方向的渗透系数普遍地大于水平方向的渗透系数；当吸力小于57 kPa时，随着吸力的增大，竖向渗透系数与水平向渗透系数的差值减小。通过观测黄土的结构，得出黄土结构对其渗透性有重要影响。

Study of the anisotropic permeability and mechanism of Q3 loess

The permeability of unsaturated loess is an important part of its properties.The research on loess permeability in different directions is particularly important to determine the range of loess collapse and the study of loess landslides caused by the infiltration of water in the loess.So,the anisotropic permeability and mechanism of Q3 loess are studied.The test samples are the undisturbed Q3 loess with obvious anisotropy from a building site in Xi’an city.The matrix suctions at different volumetric water contents and in different directions are measured with tensiometer.The saturated hydraulic conductivity is measured by falling head permeability test.The results show,while tensiometer is inserted vertically and paralleling with soil layer into samples,that the suctions are very close as the volumetric water content is between 0.23 and 0.41;and the saturated hydraulic conductivity in vertical direction is 4.02 times as that in horizontal direction.Further,the correlation function between the hydraulic conductivity and suction for unsaturated loess in vertical and horizontal directions is obtained by the soil-water characteristic curve based on the measured suctions.It can be obtained that the hydraulic conductivity reduces/increases with the matrix suction increases/reduces in both directions of the loess.The hydraulic conductivity in vertical is generally higher than that in horizontal.The difference of hydraulic conductivity between vertical and horizontal directions reduces with the matrix suction increases when matrix suction is less than 57 kPa.Structure observation shows that the anisotropy of loess structure has a significant effect on the anisotropic permeability.