Transcript Lecture11_rheology - Arizona State University

GLG310 Structural Geology
7 July 2015
GLG310 Structural Geology
sd is differential
stress
-Engelder, 1993,
Stress regimes in
the lithosphere,
Princeton Univ.
Press
GLG310 Structural Geology
Rheology:
“science of deformation and flow
of matter”
or
relationship between stress and
strain
7 July 2015
GLG510 Advanced Structural Geology
Idealized Elastic Material
Linear relationship
between force and
extension (Hooke,
1676):
• Ut tensio sic uis
• As extension so the
force
• Analogous to spring
constant
http://www.see.leeds.ac.uk/structure
/rheology/hooke.htm
GLG310 Structural Geology
E (young’s modulus)
= d sa/d ea
Units of stress
7 July 2015
-Pollard and Fletcher,
2005
GLG510 Advanced Structural Geology
http://silver.neep.wisc.edu/~lakes/PoissonIntro.html
7 July 2015
GLG310 Structural Geology
Axial versus
transverse
deformation
sa = f/A
ea = (b-B)/B
sp = 0
ep = (w-W)/W
n = - ep / e a
(Poisson ratio)
Measures
compressibility
7 July 2015
GLG510 Advanced Structural Geology
Idealized Elastic Material
Stiffness and strength
“Lest there be any possible, probably, shadow of
doubt, strength is not, repeat not, the same thing as
stiffness. Stiffness, or Young’s modulus or E, is
concerned with how stiff, flexible, springy or floppy
a material is. Strength is the force or stress needed to
break a thing. A biscuit is stiff but weak, steel is stiff
and strong, nylon is flexible (low E and strong),
raspberry jelly is flexible (low E) and weak. The two
properties together describe a solid about as well as
you can reasonably expect two figures to do.”
(Gordon, New science of strong materials, 2006)
7 July 2015
GLG510 Advanced Structural Geology
http://www.see.leeds.ac.uk/structure/rhe
ology/inelastic.htm
Plasticity
• Steady deformation at yield strength
Plasticity
• Steady deformation at yield strength
Viscosity
• Strain rate proportional to differential stress
7 July 2015
GLG510 Advanced Structural Geology
7 July 2015
GLG310 Structural Geology
Variations in mechanical behavior
http://www.youtube.com/watch?v=GxdfoJoWNE4
7 July 2015
GLG310 Structural Geology
Rock deformation experiments
7 July 2015
GLG310 Structural Geology
7 July 2015
GLG310 Structural Geology
GLG310 Structural Geology
http://www.cast.com.sg/s_soil.html
http://www.youtube.com/watch?v=n4ZAb-p-dIw
7 July 2015
GLG310 Structural Geology
Rocks can flow: salt ascends
through overlying sediments
because it is bouyant
http://maydamedia.com/Images/Chapter11/Chart11.1.jpg
7 July 2015
GLG310 Structural Geology