CIV1499HS, 2005
Material Fracture Dynamics: Experimental Methods
Graduate Course Outline
Fractures play a major role in the strength and behaviour of materials at all
scales from global earthquakes in rock to grain scale microcracks within
individual crystals. Mechanically, cracks make materials more compliant and
influence fluid flow. A key consequence of fractures (both density and alignment)
is their significant influence upon elastic wave velocity and the development of
anisotropy in materials. This course will focus on the experimental imaging of
microcracks and fractures in rock and rock like materials.
Theoretical Overview (1 hour/week):
The course will provide a theoretical framework for the geophysical
interpretation of fractured materials including, continuum mechanics, linear
fracture mechanics, effective medium theory, poro-elasticity and plasticity. The
objective for the lectures/tutorials is to facilitate the interpretation of the data
collected in the experimental part of the course.
Experimental Laboratory Investigation (3 hours/week):
Lab 1 of the course will involve the measurement of elastic wave velocities
in 4 different rock types (Westerly granite, a Canadian Shield gneiss, Carrara
marble and Fontainebleau sandstone) as a function of thermal loading in dry and
wet conditions on cubic samples. The objective is to monitor the evolution of
microcrack density, elastic wave anisotropy and shear wave splitting as a
function of thermal cracking and saturation. Experimental data will be compared
to theoretical and numerical models of fractured media.
Lab 2 of the course will involve using Acoustic Emission (AE) techniques
to study the evolution of failure processes under Mode I fracture propagation
using a Cracked Chevron Notch Brazilian Disc test. A practical introduction to
earthquake seismology techniques will be given including: (1) source location
methods; (2) auto-picking techniques; (3) frequency filtering; and (4) source
mechanism calculation.
Lab 3 of the course will involve an experiment using both AE and velocity
measurements on a concrete structure several meters in size.
The
measurements will be used to image and interpret the fracture growth induced in
the structure as a result of changing load conditions. Interferometry methods will
be applied to velocity measurements along raypaths passing through regions
where cracks are developing. Physical examination of the fractures will be used
to validate interpretations. Differences in the equipment used in this larger scale
experiment, compared to the earlier smaller scale experiments in rock and global
scale monitoring will be discussed.
Assessment:
Three laboratory appendices compiling experimental results (10% each)
will be handed back after each of the three labs. A final report, with a title of
‘Imaging of microcracks and fractures in rock and rock like materials’, will be
produced. This will be written in the form of a journal paper, and will include 10
figures from the labs, and will be a maximum of 15 pages. It will count for 30% of
the final grading. A final examination at the end of the course will count for 40%
of the final grading.
Course Instructors:
Professor Paul Young, Dr. Alex Schubnel, Dr. David Collins and Dr.
Farzine Nasseri. Web – ‘http://www.lassondeinstitute.utoronto.ca/young/’.
Venue and Time for Course:
Lectures in MB232, 2-3pm every Tuesday, Laboratory in MB108 3-6pm
every Tuesday. The first lecture and lab start Tuesday January 11 in MB 232 at
2pm.
Selected References:
• Fault mechanics and transport properties of rocks, edited by B.Evans
and T-F.Wong, Academic Press, London, 475-503, 1992.
• Fracture mechanics of rocks, edited by K.Atkinson, Academic Press,
London, 475-503, 1987.
• Fracture of brittle solids, B.Lawn, Cambridge Solid State Science series,
Cambridge, UK, 1975.
• Introduction to the Physics of rocks, Y.Guéguen and V.Palciauskas,
Princeton University press, 1994.
• Mechanics of earthquakes and faulting, C.Scholz, Cambridge University
press, 2002 (2nd edition).
• Mechanics of fluid saturated rocks, edited by Y.Guéguen and M.Boutéca,
International Geophysics Series, Elsevier Academic Press, vol.89, 2004.
• The Rock Physics Handbook, Mavko G., Mukerji T., and Dvorkin, J.,
329pp., Cambridge University Press, 1998.
• Journal of Geophysical Research, American Geophysical Union.
• International Journal of Rock Mechanics, Elsevier.