Apertures rough fractures

Geometrical factors and properties Rock fracture networks and their characterization and representation Rock fracture properties (aperture, roughness, gouge production, filling, conductivity, storativity) Variability and representability of network connectivity... 

Here, i// is the surface roughness (surface area per unit area in cross section) of the fracture walls, p is fluid density in g cm-3, and the aperture 8 is taken in cm. For our purposes, it is sufficiently accurate to choose a value of 2 for 1// and set p to 1 g cm-3. In a fracture with an aperture of 10 cm, for example, each kg of water is exposed to 400 cm2 of quartz surface. 

Fig. 1. Empirical relation between joint roughness (JRC) and the hydraulic (e) and mechanical (E) fracture aperture (after Barton et al., 1985).

The fact that this model considers elastic and inelastic fracture aperture or closure has already been discussed in the literature. For instance, Renner et al (2000) investigated the behaviour of fractured argillaceous rocks including permeability variations induced by changes in confining pressures. In this work crack dimensions and permeability are correlated by means a model that takes into account elastic crack closure and crack closure controlled by inelastic processes. This later is explained by asperity indentation when rough crack walls contact each other. 

Su et al. 27) conducted a series of laboratory tests using dyed water supplied into two Afferent setup models (1) a transparent replica (about IS-cm wide by 30-cm long) of a natural, rough-walled rock fracture from the Stripa Mine, Sweden, for inlet conditions of constant pressure and flow rate, over a range of inclination angles, and (2) parallel glass plates with three types of apertures. In these experiments water was supplied fiirough file whole width of a fiacture model. 

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