Identification of preferential flow effects on hydraulic conductivity measurements using a fluorescent tracer

Core samples were collected from fractured and unfractured zones within fin e-grained, unconsolidated mine tailings. The hydraulic conductivity of the core samples was measured in a constant-head permeameter. A fluorescent dye tracer was added to the constant-head reservoir in the permeameter. The te sts were run for approximately 48 h, then the cores were sectioned to obser ve the distribution of dye. Flow through the fractures results in hydraulic conductivity measurements up to one order of magnitude greater than that o f unfractured tailings. Observations of the dye distribution in samples fol lowing permeameter measurements are used to identify cases where preferenti al flow in fractures has influenced the hydraulic conductivity measurements . The dye tracer distribution also indicates where measurement errors may b e suspected due to flow leakage around the core sample.