Analysis of permeability characteristics using the homogenization analysis

Fracture geometries have strong influence on permeability characteristics in hard rock mass. It is important to identify accurate fracture geometries, especially roughness, aperture to calculate permeability coefficients. The detailed measurement of fracture roughness was conducted with a confocal laser scanning microscope (CLSM). Two types of analysis was performed to compute an accurate permeability coefficient along a rough fracture in consideration of fracture geometries: (1) quantitative analysis of roughness components using a spectral analysis and (2) homogenization analysis to calculate a permeability coefficient considered with permeability characteristics both in micro-scale and macro-scale. The homogenization analysis is a new type of perturbation theory developed to characterize the behavior of a micro inhomogeneous material with a periodic microstructure. Therefore, it is possible to analyze accurate permeability characteristics reflected on local effect of facture geometries. According to the computation results, the C-permeability coefficients that calculated by the homogenization analysis on each rough fracture model indicate irregular distribution without following the relationship of the cubic law. It clearly proves that permeability characteristics are strongly dependent on condition of fracture roughness and aperture variation. Moreover, it should be noted that the homogenization analysis draws more accurate result than the preexisting equations of permeability calculation.