Geology Resolving stresses on a plane

Outline Resolving stress on a plane Determining maximum shear stress Class problem

Stress

Normal and Shear Stresses  is defined as the angle from horizontal to the plane A’. Counterclockwise is positive (+).

Solving for Shear Stress

Solving for Normal Stress

Solutions for Normal & Shear Stresses

Calculating Maximum Shear Stress For what  value is the shear stress greatest?

Calculating Maximum Shear Stress For what  value is the shear stress greatest?  = 45° or  / 4 /4/4/4/4  F A

Class Problem Find the  dip value of the plane such that  s is minimized and  n maximized. A F Draw the plane on the block figure.

Class Problem A F Draw the plane on a block figure.  Find the  dip value of the plane such that  s is minimized and  n maximized.

The Relationship Between Stresses and   0 /4/4 /2/2  nn ss F / A = 1

References Slide 1 Twiss, R. J. and E. M. Moores, Structural Geology, W. H. Freeman & Co., New York, 532 p., 1992.