The fracture tensor is a combined measure of joint geometry parameters. The
possible relations between the properties of the fracture tensor and the h
ydraulic properties of jointed rock including the equivalent continuum beha
vior are investigated in this paper through numerical experiments performed
at the two-dimensional level incorporating joint networks with two joint s
ets. The possibility of a nonzero average block permeability and the equiva
lent continuum behavior of a joint system can be expressed with the help of
the first invariant of fracture tensor (F-o). A threshold value of F-o (to
achieve nonzero block permeability) between 3 and 6 and a cutoff value of
F-o (to achieve equivalent continuum behavior) between 10 and 30 were obtai
ned for the joint geometry configurations studied in the investigation. Bot
h the threshold value and the cutoff value of F-o were found to depend on t
he relative orientation of joint sets. Joint systems with low relative orie
ntation angles (for systems with only two joint sets) and low densities do
not show hydraulically equivalent continuum behavior. A nonlinear relation
seems to exist between the directional permeability and the fracture tensor
component for the connected joint configuration when rock blocks contain o
nly minor discontinuities. For rock blocks containing major discontinuities
, this relation becomes linear.