Publications Details
Impact of fracture coatings on the transfer of water across fracture faces in unsaturated media
Ground water flow in unsaturated, fractured rock is often assumed to be dominated by the porous matrix component. This is frequently based on the argument that water flowing in the fractures is rapidly imbibed into the rock matrix by capillary suction forces with negligible resistance to uptake at the matrix-fracture interface. However, the existence of a low-permeability mineralized layer or coating at this interface may substantially reduce matrix imbibition and consequently result in fracture-dominated flow. To test this concept, four tuff samples containing natural fractures were obtained from tuff formations in southern Nevada. By performing imbibition experiments into the matrix rock, across a mineralized fracture face and then across a fresh uncoated fracture face, water uptake as a function of time and coating was measured. A relatively simple model has been developed to describe the imbibition behavior. 6 refs.