1 ABSTRACT
The calibration and validation of computer simulation models used to estimate fluid flow and solute transport through variably-saturated discrete fracture networks is a necessary step for performance assessment of subsurface geologic hazardous waste storage facilities. Methodologies for estimating parameters which govern fluid flow through fractured rock are presented. The methodologies include water infiltration and air flow tests on exposed rock surfaces, subsurface cross-borehole air flow and air-phase tracer tests along fractures, and water intake into fractures from slanted boreholes in unsaturated rock. The techniques demonstrate the feasibility of characterizing water flow through saturated fractures and air flow through unsaturated fractures. Techniques to estimate fluid flow parameters in variably saturated rock have not been demonstrated.
2 INTRODUCTION
Intermediate between laboratory-scale experiments and macro-scale characterization of large geologic features lies a class of meso-scale field experiments which are not only useful for performing confirmatory analysis of theoretical models, but also for providing parameters necessary for macro-scale computer models. While procedures for characterizing flow and transport through unsaturated soil materials have been examined extensively in the fields of soil physics, soil mechanics and others, some of the laboratory techniques are readily transferable to the assessment of rock matrix properties using rock cores while others require modifications to account for the normally lower porosities and permeabilities of consolidated geologic media and the difficulties of instrument emplacement and of adequate instrument/rock contact. Laboratory-scale experiments, however, are inadequate for examining the water conducting and contaminant transport properties of natural fracture systems. These properties must be assessed in situ utilizing various testing procedures which have only recently been examined for unsaturated fractured rock, and then only for fluid flow and not contaminant transport. The methods to be described in this paper use either air or water injection procedures to characterize individual fractures and fracture connections. The methods have been field tested at volcanic tuff sites near Tucson, Arizona.
3 FORMULATION OF LIQUID AND GAS FLOW THROUGH NATURAL FRACTURES
The fluid mass flow rate, vm (in kg/m2s), for both liquids can be expressed by (e.g., see Muskat, 1946): (mathematical equation)(available in full paper)
