On water infiltration in rough-walled fractures

A serious concern regarding the suitability of Yucca Mountain for nuclear waste isolation is the potential for rapid transport of dissolved radionuclides along localized preferential flow paths in fractures. Hydrogeologic and geochemical studies at Rainier Mesa have provided strong evidence for fast water flow through unsaturated fractured rock. These observations cannot be reconciled with conceptual models of uniform infiltration or models that postulate strong capillary imbibition effects from the rock matrix on water flowing in fractures. Alternative concepts have been proposed such as the 'weeps model', which is supported by observations of gravitationally unstable flow (fingering) in heterogeneous fractures. In an effort to explore the conditions and characteristics of preferential flow we have performed physical and numerical experiments in rough-walled fractures