Modelling of DNAPL behavior in vertical fractures

This paper describes an investigation into DNAPL behavior in saturated, smooth-walled, vertical fractures. A new theoretical model, which accounts for contact angle dependency on velocity and pinning of the DNAPL-water interface at the walls of the fracture, is developed. Centrifuge scaling laws relevant to the problem are derived through partial inspectional analysis of the model equations. A series of centrifuge tests mimicking DNAPL infiltration into circular fractures of different diameters is described. Comparison of the centrifuge test data with prototype experiments is used to verify the centrifuge scaling relationships. Selected centrifuge test data are also used to validate the new theoretical model. The work demonstrates that the criterion for DNAPL to infiltrate a fracture can be modeled using the geotechnical centrifuge. However, the infiltration kinetics within a fracture are not always properly scaled. The work clearly illustrates the influence of contact angle variability, pinning forces and inertia on the physics of DNAPL behavior in an idealized fracture.