154 Permeabilitywhen the REV value is of the order of 8 m3. More mathematical ap-
proaches could be used to evaluate the REV if justified.
We emphasize that the data in this question, and our interpretation,
have been presented to illustrate the concept of the REV. In another case,
the mean might increase, decrease or oscillate as the tested volume in-
creases. Also, if the rock mass is heterogeneous, and hence its measured
value changes with location, it is possible that no REV will be identified
because the rock properties could be changing with location faster than
the REV is being reached by increasing the sampling size. Numerical
simulation of fracture patterns and the associated fracture connectivity
and REVS was pioneered by Long (1983) '.
49.8 The values and directions for the principal hydraulic conduct-
ivities in a dolomitic rock, shown below, were obtained from back
analysis of induced drainage discharges at the Morro da Usina
Mine, Vazante District, State of Minas Gerais, Brazil '. These are
the mean principal hydraulic conductivities for a rock mass volume
greater than 3 km3. What geological circumstances could cause
these values and orientations?270180
$( K max = 1.596E-4 m/s. K min = 3.042E-6 m/s
- K int = 5.9278-6 m/s
NLong J. C. S. (1983) Investigation of equivalent porous medium permeability in networks of'I The authors are grateful to Prof. E. Quadros and Dr. E 0. Franciss for permission to
discontinuousfiactures. PhD Thesis, University of California, Berkeley.use this example.