Comparative Evaluation of Selected Continuum and Discrete-Fracture Models: Emphasis on Dispersivity Calculations for Application to Fractured Geologic Media, Creston Study Area, Eastern Washington.

摘要

Transverse dispersivity calculated using an analytical solution to the dispersion equation is compared to transverse dispersivity derived using a discrete-fracture model for four cases involving two sets of parallel, planar, continuous fractures intersecting at various angles. The results demonstrate that dispersivity calculated by a discrete-fracture model agrees well with theory. Scale effects of transverse dispersivity indicated that a relatively constant value was reached after particles had traveled about 10 times the fracture spacing of the most widely spaced fracture family. A field example compares dispersivities estimated from two natural-gradient tracer tests to dispersivities calculated from rock core and other data. The example demonstrates that there is good agreement between the theory and actual field tracer tests.