1
Rationale of the Triaxial Method
(1) Stresses at failure are a function of
confining pressure
Failure envelope
is defined by
Cohesion and φ
Plots of Mohr Circles at Failure
(2) Plots of Maximum Shear and Normal Stresses due to a
Uniform Circular Vertical Load (3) Failure will occur if the combinations of shear
stresses and normal stresses fall outside of the
failure envelope for the pavement material.
(4) For a given combination of shear and normal
stresses, the required cohesion ( C ) and friction
angle (φ) for the material such that the material
would not fail can be determined.
(See next figure)
Determination of the Required C and φto Prevent
Failure for a Combination of Shear and Normal Stresses (5) Plots of the Required C for Different φvalues to
Prevent Failure under a Uniform Vertical Load of
Radius of R and Pressure of P
The critical
condition
occurs at
the surface.
Thus only
failure at
the surface
needs to be
considered.
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