延安Q3原状黄土渗透各向异性及微结构分析

为研究原状马兰黄土的渗透各向异性，以延安削山造地重大工程开挖所揭露的完整黄土剖面中的马兰黄土层为研究对象，采用室内变水头渗透试验获取不同埋深不同渗流时长原状黄土垂直向和水平向的渗透系数，并对试验前后黄土试样垂直向和水平向SEM（scanning electron microscope）电镜扫描结果进行分析，从微观结构上揭示原状马兰黄土结构各向异性的原因。结果表明：原状黄土垂直向和水平向饱和渗透系数具有显著各向异性，且垂直向和水平向渗透系数都随渗流时间的持续而减小，各向异性渗透性能在时间尺度上具有某种衰减关系；同时，原状黄土各向异渗透性能随埋深的增大而逐渐减弱；土颗粒结构的接触、排列方式是导致黄土原生各向异性的根本原因，也是导致渗流初始阶段渗透系数各向异性的原因，而渗流作用产生的次生结构各向异性则使渗透系数各向异性在时间尺度上表现得更为明显。

Permeability Anisotropy and Microstructure of Yan'an Q3 Loess

In order to study the anisotropic permeability of undisturbed loess, Yan'an Q₃ loess with obvious anisotropy was chosen as the research object. The vertical and horizontal permeability coefficients of different deep-buried undisturbed loess were measured by variable water head permeability tests in laboratory. The results showed that the vertical permeability coefficient of undisturbed loess was larger than the horizontal permeability coefficient of the same horizon. In addition, both vertical and horizontal permeability coefficients of undisturbed loess decreased with the increase of burial depth of loess, and the anisotropy of undisturbed loess was weakened as the burial depth increased, which indicates that anisotropic undisturbed loess gradually become isotropic with the increase of buried depth. Furthermore, in order to investigate the anisotropy of undisturbed loess from microstructure, the longitudinal and transversal sections of undisturbed loess in different buried depths were characterized by SEM (scanning electron microscopy). It was found that the contact and arrangement of soil particles are the fundamental factors resulting in the anisotropic loess.