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I. Continuum Models of Material Behavior
A. Continua: assumption that rocks behave as cohesive mechanical units,
averaging out effects of local anisotropies and polycrystalline nature
B. Rheological Models for Rock
1. Elastic Behavior
a. linear elastic behavior: material deforms by an amount
proportional to the applied stress
(1) when stress is released, material strain recovers to original
undeformed state
(2) Young's Relations
(a) Stress = E(strain)
b. Similar to Hooke's law for a spring (ideal elastic)
(1) Force = k(spring displacement)
c. Stress-strain diagram
(1) normal stress on y axis
(2) lengtening or shortening strain on x axis
(3) true elastic solid: linear relationship
2. Viscous Behavior
a. example fluid behavior
(1) stress applied to fluid: fluid deformation (motion)
(a) remove stress, fluid stops, but does not recover to
initial state
b. Viscous behavior: nonrecoverable strain
(1) Newtonian fluid
(a) linear relation between stress and strain rate
(b) > stress, > rate of strain (dx/dt)
(c) Newtonian stress-strain diagram
i) stress = y-axis
ii) strain rate = x-axis
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