Structural Effects on Effective Conductivity of Compacted Clays

In this study, an electromagnetic property, the effective (electrical) conductivity, of two clayey soils has been measured at different moisture contents and in different directions. Scanning electron microscopy (SEM) was used to evaluate the structural effects on effective conductivity, and X-ray diffraction (XRD) was used to perform qualitative analysis on the mineralogical makeup of clay fraction. At the optimum moisture content, the results showed a significant difference between the effective conductivity measured in the horizontal direction and that measured in the vertical direction with the latter being smaller. The SEM results showed that this was attributed to the highly preferred orientation of clay particles and their decreased tortuosity in the vertical plane (horizontal direction) and the increased tortuosity in the horizontal plane (vertical direction). At four percent dry of optimum, the difference in the electrical conductivity measured in two directions was reduced by up to 45%. SEM results showed that the clay particles were more randomly oriented and only had a slight preferred orientation normal to the axial load.