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Geology 3120 - Geology 3120 - Resolving stresses on a planeResolving stresses on a plane
OutlineOutline
• Resolving stress on a plane
• Determining maximum shear stress
• Class problem
StressStress
Normal and Shear StressesNormal and Shear Stresses
is defined as the angle from horizontal to the plane A’. is defined as the angle from horizontal to the plane A’.
Counterclockwise is positive (+). Counterclockwise is positive (+).
Solving for Shear StressSolving for Shear Stress
Solving for Shear StressSolving for Shear Stress
Solving for Shear StressSolving for Shear Stress
Solving for Shear StressSolving for Shear Stress
Solving for Normal StressSolving for Normal Stress
Solving for Normal StressSolving for Normal Stress
Solving for Normal StressSolving for Normal Stress
Solving for Normal StressSolving for Normal Stress
Solutions for Normal & Shear Solutions for Normal & Shear
StressesStresses
Calculating Maximum Shear StressCalculating Maximum Shear Stress
For what For what value is the shear stress greatest? value is the shear stress greatest?
Calculating Maximum Shear StressCalculating Maximum Shear Stress
For what For what value is the shear stress greatest? value is the shear stress greatest? = 45° or = 45° or //44
//44
FF
A
Class ProblemClass Problem
Find the Find the dip value of the plane such that dip value of the plane such that ss is minimized and is minimized and
n n maximized.maximized.
A
FF
Draw the plane on Draw the plane on
the block figure.the block figure.
Class ProblemClass Problem
A
FF
Draw the plane on a Draw the plane on a
block figure.block figure.
Find the Find the dip value of the plane such that dip value of the plane such that ss is minimized and is minimized and
n n maximized.maximized.
The Relationship Between Stresses and The Relationship Between Stresses and
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.60
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 /4/2
n
s
F/A = 1
ReferencesReferences
Slide 1
Twiss, R. J. and E. M. Moores, Structural Geology, W. H. Freeman & Co., New York, 532 p., 1992.
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