Permeability and Seepage Flow - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 157

leading to a specifi c storage coeffi cient of

Intact rock is assumed to be impermeable.

Figure 6.20 Joint aquifer and pore aquifer, parameters

On the other hand, a pore aquifer consisting of porous sandstone is considered. In the liter-
ature for sandstone exhibiting a permeability of some 1 10 -6 m/s, total porosities varying

from 6% to 30% can be found. An effective porosity of n IR = 0.1, corresponding to 10%
of the pore aquifer, according to (6.60) leads to a specifi c storage coeffi cient of
S 0,IR = 0.01 m -1 (Fig. 6.20, right). A discontinuity system of the pore aquifer is not
accounted for.

⋅

For both aquifers, the lowering of the water table by a well of radius r 0 = 0.2 m is calcu-
lated. The thickness of the aquifer penetrated by the well is assumed to be H = 10 m. A
pumping rate of Q P = 0.02 l/s = 2 10 -5 m3/s is chosen to achieve a maximum drawdown ⋅

of Δ h 0 = 2 m below the undisturbed water table (Fig. 6.21).