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Fig. 2. (a, c, e) Schematic view of polarizing cells based on the granular model and (b, d, f) equivalent pore sketches for dense (right) and loose (left) packings of particles at different water content: (a, b) full saturation, (c–f) partial saturation. Gray and white areas indicate water and particles, respectively. In the saturated case (a, b), water-filling intergrain spaces can be considered large pores. Areas of grain contact, where the water is in a closer bond on the grain surface, can be considered throats. In the partially saturated case (c, d), the water film at the surface of moistened grains can be considered a narrow passageway for electric current (throats). Areas of grain contact, where water is more abundant because of surface tension (water "rings"), can be viewed as large passageways (similar to large pores in the saturated case). With further desaturation, cells continuously loose water from the grain contact area and both thickness and diameter of the water rings decrease (e, f).
