- Who: Laura J. Pyrak-Nolte, Purdue University
- What: Download the flyer (pdf)
- Where: Building 66 Auditorium
- When: 10:30 am to 12:00 noon, October 25, 2013
- Why: About the Distinguished Scientist Seminar Series
More Information
Dr. Laura J. Pyrak-Nolte is a Professor in the Physics Department,
College of Science, at Purdue University. She holds courtesy
appointments in the School of Civil Engineering and in the Department of
Earth, Atmospheric and Planetary Sciences, also in the College of
Science. Prior to arriving at Purdue in 1997, she was an Assistant
Professor at the University of Notre Dame in the Department of Civil
Engineering and Geological Sciences. Dr. Pyrak-Nolte holds a B.S. in
Engineering Science from the State University of New York at Buffalo, an
M.S. in Geophysics from Virginia Polytechnic Institute and State
University, and a Ph.D. in Materials Science and Mineral Engineering
from the University of California at Berkeley. Her interests include
applied geophysics, experimental and theoretical seismic wave
propagation, rock mechanics, micro-fluidics, particle swarms, and fluid
flow through Earth materials. In 1995, Dr. Pyrak-Nolte received the
Schlumberger Lecture Award from the International Society of Rock
Mechanics. She received Young Investigator Awards from the National
Science Foundation and the Office of Naval Research, and in 2001, Purdue
recognized Dr. Pyrak-Nolte’s accomplishments with a University Scholar
Award. In 2012, she was appointed to the Department of Energy Earth
Sciences Council, the Board of the American Rock Mechanics Association
and to the Council for the International Society of Porous Media. In
2013, she was made a Fellow of the American Rock Mechanics Association.
Abstract
The hypothesis that the hydraulic, mechanical and seismic properties
of fractures are all interrelated has been indirectly implied by
research performed by the hydrology, geomechanics and geophysics
communities—but with each community providing a partial view into the
behavior of fractures and fracture networks. For example in the
hydrology community, fluid flow through fractures and fracture networks
has established that fluid flow through a fracture depends on length
scales associated with the size and spatial distribution of the
connected apertures (that depend on stress) within a fracture or
fracture network. In the geomechanics community, it has been
independently shown that fracture deformation is controlled by
length-scales associated with the size and spatial distribution of
contacts between the two surfaces of a fracture and depends on the
loading condition. On the other hand, the geophysics community views
fractures either as discrete features that give rise to converted modes,
or as sources of moduli reduction that depend on stress-dependent
fracture specific stiffness and the wavelength of the seismic probe.
Fracture specific stiffness, in turn, depends on both contact area and
aperture distribution of the fracture, which comes full circle back to
hydrology and geomechanics. Ultimately, all three fields have
demonstrated that each physical property of interest to their community
depends on the geometry of the voids and contact area that define the
fracture, and thus should be implicitly linked through the fracture
geometry.
In this presentation, results from a finite-size scaling analysis are
presented that reveal a fundamental scaling relationship between
fracture stiffness and fracture fluid flow. Computer simulations
extract the dynamic transport exponent that is used to collapse the
flow-stiffness relationship onto a universal scaling function. Near the
critical percolation threshold, the scaling function displays a break
in slope that is governed by the topology of the stressed flow paths.
The resulting hydromechanical scaling function provides a link between
fluid flow and the seismic response of a fracture, which suggests that
seismic techniques may provide a means for remote sensing of fracture
permeability. To fulfill this potential, deeper understanding of the
origins and dynamics of fracture seismic stiffness is still required.
Recent results will be presented on the seismic response of the
intersections between multiple fractures, which represent a newly
uncovered contribution to the compliance of a rock mass.