A two-dimensional model of fracture permeability normal to bedding in layer
ed rock with orthogonal, bed-delimited fractures is investigated. Steady-st
ate, saturated laminar flow is assumed. Permeability is assumed to be a fun
ction of apertures and flow path lengths in an otherwise impermeable matrix
. Bedding planes or other separations between layers are modeled as fictiti
ous interlayers to render a layered fractured rock mass equivalent to a lay
ered porous medium. Layer, or bed-normal permeability is quantified in term
s of readily available field data, using a probability model to represent f
racture connectivity between layers. The bed-normal permeability is shown t
o depend on fracture spacing and aperture, layer spacing and bedding plane
aperture, and to be scale-dependent. Numerical investigation and comparison
with field data indicates that the derived expression is useful for estima
ting layer-normal permeability. (C) 2001 Elsevier Science Ltd. All rights r
eserved.