Relating Hydraulic-Electrical-Elastic Properties of Natural Rock
Fractures at Elevated Stress and Associated Transient Changes of
Fracture Flow
Abstract
Monitoring the hydraulic properties within subsurface fractures is
vitally important in the contexts of geoengineering developments and
earthquakes. Geophysical observations are promising tools for remote
determination of subsurface hydraulic properties; however, quantitative
interpretations are hampered by the paucity of relevant geophysical data
for fractured rock masses. This study explored simultaneous changes in
hydraulic and geophysical properties of natural rock fractures with
increasing normal stress and correlated these property changes through
coupling experiments and digital fracture simulations. We show that
electrical resistivity is linked with permeability and flow area
regardless of fracture roughness, whereas elastic wave velocity is
roughness dependent. We also are able to categorize fracture flow
patterns as aperture-dependent, aperture-independent, or disconnected
flows, with transitions at specific stress levels. Elastic wave velocity
offers potential for detecting the transition between aperture-dependent
flow and aperture-independent flow, and resistivity is sensitive to
detect the connection/disconnection of the fracture flow.