Wetting Front Instability in an Initially Wet Unsaturated Fracture

by M. J. Nicholl, Sandia Natl Lab, Albuquerque, United States,
R. J. Glass, Sandia Natl Lab, Albuquerque, United States,
H. A. Nguyen, Sandia Natl Lab, Albuquerque, United States,

Document Type: Proceeding Paper

Part of: High Level Radioactive Waste Management 1993


Experimental results exploring gravity-driven wetting front instability in a pre-wetted, rough-walled analog fracture are presented. Initial conditions considered include a uniform moisture field wetted to field capacity of the analog fracture and the structured moisture field created by unstable infiltration into an initially dry fracture. As in previous studies performed under dry initial conditions, instability was found to result both at the cessation of stable infiltration and at flux lower than the fracture capacity under gravitational driving force. Individual fingers were faster, narrower, longer, and more numerous than observed under dry initial conditions. Wetting fronts were found to follow existing wetted structure, providing a mechanism for rapid recharge and transport.

Subject Headings: Cracking | Infiltration | Fluid flow | Moisture | Hydraulic fracturing | Analogs | Waste disposal

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