Coupling of Stress-Strain Behavior and Seepage Flow - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 168

Figure 7.3 Aperture changes of discontinuities adjacent to a tunnel due to excavation

7.2 Permeability of a Discontinuity as a Function of Stress

7.2.1 Permeability of a Discontinuity as a Function of Normal Stress
If a compressive normal stress

σ n is applied to a discontinuity fi lled with water the mean

aperture is a function of joint closure δ n,D :

(7.1)

in which is the mean aperture for σ n = 0 referred to as “initial aperture”, Δ p w is

the excess joint-water pressure and κ h,D is the hydraulic degree of separation defi ned in

(6.30).
In the following, steady-state conditions only are assumed: p w = 0. The build up and

dissipation of excess joint-water pressure with time, known as “consolidation”, will not
be considered in this topic. The interested reader in this respect is referred to the related
literature covering porous rock, jointed rock and rock with double porosity: Biot 1941,
Biot 1955, Duguid & Lee 1977, Jaeger & Cook 1979, Walsh 1981, Khalili-Naghadeh
& Valliappan 1991, Valliappan & Khalili-Naghadeh 1991, Detournay & Cheng 1993,
Fabre & Gustkiewicz 1997, Chen & Bai 1998, Liu et al. 1999, Tang et al. 2002, Zhang et
al. 2003, Lion et al. 2004, Min et al. 2004b, Zhao & Chen 2006, Chen et al. 2007, Yang
et al. 2007.

Δ

Setting Δ p w = 0 (7.1) can be simplifi ed as

(7.2)