AN IMPROVED FRACTAL PERMEABILITY MODEL FOR POROUS GEOMATERIALS WITH COMPLEX PORE STRUCTURES AND ROUGH SURFACES

Abstract

Permeability is a critical parameter for characterizing the migration behavior of a fluid in porous media, thus being of great importance in guiding the geotechnical engineering practice. In this study, an improved permeability model was developed on the basis of the fractal features of the porous geomaterials. It further takes into account the periodic variation of the cross-section of the pore path in the flow direction and the roughness of the pore surfaces. This model indicates that the permeability is a function of the porosity, maximum pore radius, proportion of minimum pore radius to the maximum pore radius, roughness of the capillary tube, and variation in the cross-sectional characteristics of the tube. It provides a better insight into the transport mechanism of fluids in porous geomaterials. The permeability of the model is related to the variable cross-sectional characteristics of the pore channel, i.e. the belly-to-throat ratio and the roughness, as a quadratic function. These two parameters are the key to affecting the level of permeability. The model was verified over a wide range of permeability variations by changing from high-permeability media (102 mD) to low-permeability media (10−3 mD). Accurate permeability prediction of high–low-permeability porous media can be achieved by considering the variation of parameters.