Fracture permeability normal to bedding in layered rock masses

A two-dimensional model of fracture permeability normal to bedding in layered rock with orthogonal, bed-delimited fractures is investigated. Steady-state, saturated laminar flow is assumed. Permeability is assumed to be a function of apertures and flow path lengths in an otherwise impermeable matrix. Bedding planes or other separations between layers are modeled as fictitious interlayers to render a layered fractured rock mass equivalent to a layered porous medium. Layer, or bed-normal permeability is quantified in terms of readily available field data, using a probability model to represent fracture connectivity between layers. The bed-normal permeability is shown to 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 estimating layer-normal permeability. (C) 2001 Elsevier Science Ltd. All rights reserved.