The relation between silty soil structures and their mercury porosimetry curve counterparts: fractals and percolation

Mercury porosimetry data can be interpreted in terms of soil structure usin g ideas drawn from (i) network modelling and percolation theory and (ii) fr actal geometry. We linked mercury intrusion to soil structure quantified by image analysis within a relevant common pore radius scale. We compared (i) three independent methods for computing fractal dimensions of the matrix a nd of the solid-pore interface, namely fitted square boxes method and pore chord distribution on scanning electron microscope images of soil thin sect ions, and mercury porosimetry, and (ii) two independent methods for charact erizing pore connectivity (image analysis) and percolation process (pressur e threshold from mercury porosimetry). The results from analyses of the por e size distribution by mercury porosimetry differed from those from the ima ge analysis. Mercury intrusion is controlled by both the connectivity of th e pore space network and locally by pore throats leading to larger pore bod ies. By contrast, image analysis is unaffected by pore connectivity and mea sures pore bodies. On the other hand, the chord length method might not ade quately capture the scaling properties of the solid-pore interface, whereas the mercury porosimetry data were also difficult to interpret in terms of fractal geometry because of the effects of pore connectivity. However, frac tal dimension values of both the solid phase and the solid-pore interface i ncreased as a function of clay content, whereas both percolation probabilit y values and throat radius values at the mercury percolation threshold decr eased. The results show the merit of applying both fractals and percolation theory for determining structural parameters relevant to mercury and water transport in soil.