Coupling of Stress-Strain Behavior and Seepage Flow - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 170

Figure 7.4 Mean aperture of a discontinuity as a function of normal stress (Erichsen 1987)

In the case of a normal tensile stress an opening of the discontinuity and a correspond-
ing increase in permeability takes place.

7.2.2 Permeability of a Discontinuity as a Function of Normal Compressive
Stress and Shear Stress
If a shear stress

τ res and a compressive normal stress σ n are applied to a discontinuity,

the mean aperture is a function of both the normal stress σ n and the shear displace-

ment δ s,D caused by τ res :

(7.8)

in which δ n,D ( σ n ) is the normal displacement due to σ n and δ n,D ( δ s,D ) is the normal

displacement due to δ s,D caused by τ res (Fig. 7.5). While σ n leads to a compression

δ n,D ( σ n ) > 0, the shear displacement δ s,D for a rough discontinuity leads to a dilatant

normal displacement δ n,D ( δ s,D ) < 0 (Fig. 7.5).