Permeability and Seepage Flow - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 149

Figure 6.16 Equivalent permeability tensor of a rock mass with persistent horizontal bedding-parallel
discontinuities fi lled with clay and one set of open vertical joints ending at the bedding
If the permeability of the intact rock needs to be considered, as for example in the case
of porous sandstone, the permeability tensors of the discontinuity sets can be superim-
posed with a permeability tensor
(6.45)
describing an isotropic permeability of the intact rock to obtain the equivalent rock
mass permeability (Wittke 1990). A corresponding superposition is also possible if the
intact rock's permeability is anisotropic. However, the superposition of permeability
tensors of discontinuity sets and the intact rock is only permitted for steady-state fl ow.