If you are a geotechnical engineer in what situations would you specify shear box testing as an aid to geotechnical design?

Shear box tests are used to derive the following soil properties:

1. The peak shear strengthA
2. The residual shear strength (may also be referred to as the critical state)B
3. The cohesion (where applicable)C
4. The friction angleD

A Derived by plotting the shear stress vs. horizontal strain and finding the maximum shear stress value.

B Derived as above, but from the post peak horizontal portion of the stress strain curve.

C Derived from a plot of peak shear stress vs. normal stress and is equal to the shear stress where the line of best fit intersects the shear stress axis. NB for cohesionless materials such as clean sands or gravels this value will be zero.

D Derived from same plot as C but is calculated by Tan-1((Shear stress - Cohesion) / Normal stress)).

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