FLOW CHANNELING IN HETEROGENEOUS FRACTURED ROCKS

Experimental observations and theoretical studies over the last 10 yea rs or so have demonstrated that flow channeling or preferred flow path s is a common phenomenon in fractured rocks. The reason it has come to the forefront of scientific investigation is the recent interest in p redicting solute transport in geological media as part of safety asses sment of geologic isolation of nuclear or toxic wastes. Solute transpo rt is much more sensitive to medium heterogeneity than is temperature or pressure. In this paper, experimental observations of tracer transp ort over distances ranging from centimeters' to hundreds of meters are reviewed, and theoretical efforts to explain or model these observati ons are summarized. Processes that may explain some of the experimenta l observations without the use of flow-channeling models are discussed . The paper concludes with a discussion of the implications of flow ch anneling on the practical problems related to contaminant transport in geologic systems.