Aqueous flow and transport in analog systems of fractures embedded in permeable matrix

Two-dimensional laboratory investigations of flow and transport in a fractu red permeable medium are presented. Matrix blocks of a manufactured consoli dated permeable medium were arranged together to create fractures in the sp aces between the blocks. Experiments examined flow and transport in four di fferent configurations: (1) matrix only, (2) and (3) matrix blocks containi ng single fractures of different mean apertures, and (4) a brickwork patter n setup simulating a tortuous multiple fracture network. The observed parti tioning of flow and solute concentrations suggested mass exchange between t he fractures and the matrix was occurring. An analysis of the experimental results using a discrete fracture model and a range of constant aperture mo dels showed that this approach did not capture the correct flow mechanisms. Subsequent simulations including spatial variations of the fracture apertu re were better able to describe the experimental observations and to show t hat these variations cause mass exchange between the fracture and matrix.