Stress Distribution
and all of its mysteries
I. The Bulb of Pressure
Force
I. The Bulb of Pressure
Force
“what are the
stresses at this
point?”
(boo-sinn-esk)
II. The Boussinesq Equation
A. Goal: to determine the vertical and
horizontal stresses under a point load in a
homogeneous, isotropic medium.
• Allows us to determine vertical and horizontal stresses at any point in space
• Examine the transmission and distribution of stresses in large, extensive masses
of soil.
Culvert?
II. The Boussinesq Equation
B. The Equation:
II. The Boussinesq Equation
B. The Equation:
Where v = Poisson’s
Ratio (0.48)
Also an equation for σy
6.71
If Poisson’s ratio is ~0.5, equations simplify to:
σx = 3Px2z
2π R5
σy = 3Py2z
2π R5
Your turn:
Vertical load of 2500 lb/ft2
Determine horizontal (x) and vertical (z) stresses
at X= 5, Y= 2, Z = 6