Fractal analysis of the fabric changes in a consolidating clay

Electron microscopy and mercury intrusion porosimetry studies on the fabric of clays undergoing consolidation tests have indicated that the clays have pores of different sizes and shapes. After pressure is applied to the clay samples, the larger pores change in size and shape, with the smaller pores being relatively unaffected. The size of the pores and their distribution have been determined from mercury porosimeter tests. The shape of the pores and the changes they experience during the consolidation process have received only a qualitative evaluation from the photomicrographs obtained with the scanning electron microscope. In this study, a quantitative evaluation of the shape of the pores in a clay subjected to consolidation stresses is presented. This evaluation is done using fractal theory. Fractal theory employs the concept of fractal dimension to evaluate the shape (roughness) of closed profiles such as pores. The larger the fractal dimension, the rougher is the shape of a closed profile. The fractal dimension of a pore in a clay sample undergoing consolidation changed progressively from 1.4623 (very rough pore) to 0.9856 (very smooth pore). Thus, during consolidation, the pore, besides changing in size, also experienced a change in its degree of roughness. In addition, a theoretical analysis of the influence of the shape of the pores on the rate of water flow from a saturated clay undergoing consolidation is presented.