Two-Phase (Air and Water) Flow through Rock Joints: Analytical and Experimental Study

This research study deals with the characterization of two-phase flow in a fractured rock mass. A comprehensive mathematical model with which to predict the quantity of each flow component in a single joint is developed. A joint with two parallel walls filled with layers of water and air stratified is analyzed. The effects of mechanical deformation of the joint, the compressibility of fluids, the solubility of air in water, and the phase change between fluids have been taken into account to develop analytical expressions which describe the behavior at the air–water interface. The model was calibrated using a newly designed two-phase high-pressure triaxial cell. Tests were conducted on fractured hard rock samples for different confining pressures with inlet water and inlet air pressures. As in single-phase flow, it was found both experimentally and theoretically, that the flow quantities of each phase decreases considerably with an increase in confining stress. The results also confirm that the effect of joint deformation and compressibility of fluids governs the flow volume of two-phase flow. Good agreement was obtained between the experimental data and numerical predictions. DOI: 10.1061/ ASCE 1090-0241 2003 129:10 918 CE Database subject headings: Hydromechanics; Two phase flow; Joint rocks; Surface roughness.