Mohr-Coulomb Model

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Mohr-Coulomb Model

• Short Course on Computational Geotechnics
  Dynamics
• Boulder, Colorado
• January 5-8, 2004

Stein Sture Professor of Civil Engineering Univers
ity of Colorado at Boulder
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Contents

• Idealized and Real Stress-Strain Behavior of
  Soils
• Basic Concepts of Mohr-Coulomb Model
• Mohr-Coulomb Model Modeling
• Friction Angle
• Influence of Intermediate Principal Stress on
  Friction Angle
• Drained Simple Shear Test
• How to Understand ?
• Drained Triaxial Test

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Idealized and Real Stress-Strain Behavior of Soils
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Basic Concepts of Mohr-Coulomb Model

• Bilinear approximation of triaxial test
• Basic law

for
reversible elastic strain
irreversible plastic strain f yield function
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Mohr-Coulomb Soil Modeling
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Mohr-Coulomb Soil Modeling

• Flow rule for plastic strain
• This means ,
  , etc.

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Mohr-Coulomb Soil Modeling

• a multiplier that determines the
  magnitude of plastic strains
• determines the direction of plastic
  strains
• Classical associated plasticity g f
• General non-associated plasticity g ? f
• M-C model f ? r s sin? c cos? yield
  function
• g ? r s sin? c cos? plastic potential
  function

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Mohr-Coulomb Soil Modeling
Nonlinear Failure Envelope Representation
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Mohr-Coulomb Soil Modeling
Friction Angle Definitions
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Mohr-Coulomb Soil Modeling
Strength Envelopes for a Range of Soil Types
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Mohr-Coulomb Soil Modeling
Versus Relative Density and Unit Weight
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Friction Angle
Dilatancy Angle Relationships
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in which
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for NC Clays vs. PI
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Influence of Intermediate Principal Stress on
Friction Angle
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Influence of Intermediate Principal Stress on
Friction Angle
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Drained Simple Shear Test
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How to Understand y
? ? ?i or ? ? - ?i
?i inter particle angle of friction
quartz sand ? ? ? 30o
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Drained Triaxial Test
(identical to biaxial test)