Application of Impedance Spectroscopy for Determining Fabric Anisotropy of Fine-Grained Soils

Engineering behavior of fine-grained soils is mainly influenced by its fabric structure, which is the arrangement of soil particles and distribution of the pores. For determination of soil fabric, earlier researchers have relied on instrumentation techniques such as scanning electron microscope (S EM) and mercury intrusion porosimetry (MIP). However, due to small sample size, complexities involved with the sample preparation, and destructive nature of these techniques, precise interpretation of the results becomes a challenging task. In order to overcome this, efforts were made by the authors to explore the potential of impedance spectroscopy, which is a non-destructive and non-invasive technique of characterizing the soil mass, for determining its fabric. Details of the methodology adopted to achieve this are presented in this paper, which also elaborates the setup employed to determine the electrical conductivity of the marine clay samples in their undisturbed and remolded states. Further, the observed directional dependency of electrical conductivity, i.e., electrical anisotropy, has been expressed as the anisotropy coefficient, A(e), and its potential in defining the fabric anisotropy has been demonstrated. The results have been critically examined vis-a-vis the observations from the SEM and MIP studies. The study reveals that the higher the deviation of A(e) from unity, the higher would the fabric anisotropy be, which is indicative of the fabric of the fine-grained soils.