Anisotropic hydraulic conductivity of as-compacted, bare and vegetated soils

Mostafa Gholami, Hamed Sadeghi, Pouya AliPanahi
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Abstract

Soils are generally considered anisotropic with respect to hydraulic conductivity, while the evolution of anisotropy condition is unknown for bare and vegetated soils. Therefore, the main goal of this study is to compare the anisotropic hydraulic conductivity of as-compacted, bare, and vegetated specimens. Accordingly, a series of 54 hydraulic conductivity tests were conducted in a custom-made cube triaxial permeameter. The as-compacted specimens were revealed isotropic because the loosely packed preparation procedure resulted in a dominant flocculent structure. However, a fivefold increase in the anisotropy ratio of bare specimens was measured along the isotropic loading path because of the induced surficial degradation zone formed by irrigation and desiccation processes as evident in preliminary observations and crack network analysis. The variations in anisotropy ratio vs. void ratio function of vegetated soil generally fall below the corresponding function of the bare soil. The function was revealed to have a crossed nature, varying from sub-isotropic to super-isotropic states, corresponding to the lower and upper bounds of 0.3 and 3, respectively. It was postulated that vegetation impacts the flow differently by reducing the potential of desiccation cracks, creating preferential flow through the propagation of primary roots and clogging flow channels by secondary roots.
压实土、裸土和植被土的各向异性导水率
一般认为土壤在导水率方面是各向异性的,而裸土和植被土壤各向异性条件的演变情况尚不清楚。因此,本研究的主要目标是比较原压实土、裸土和植被土试样的各向异性导水率。因此,在定制的立方体三轴渗透仪中进行了一系列共 54 项导水率测试。压实后的试样显示为各向同性,因为松散包装的制备过程导致了主要的絮状结构。然而,在各向同性加载路径上测得的裸试样各向异性比增加了五倍,这是因为灌溉和干燥过程形成了表层降解区,这在初步观察和裂缝网络分析中显而易见。植被土壤各向异性比与空隙率函数的变化一般低于裸土的相应函数。结果显示,该函数具有交叉性质,从次各向同性状态到超各向同性状态,分别对应于 0.3 和 3 的下限和上限。据推测,植被通过降低干燥裂缝的可能性、通过主根的繁殖产生优先流动以及通过次生根堵塞流动通道,对流动产生不同的影响。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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