Mogi-Coulomb Criterion


Definition - What does Mogi-Coulomb Criterion mean?

The Mogi-Coulomb criterion is used in wellbore stability analysis, understanding rock strength under true triaxial condition. It is found that the intermediate principal stress (σ2) influences the ultimate strength of a rock.

Alternatively, in the Mohr-Coulomb criterion, only the maximum (σ1) and minimum (σ3) principal stresses are considered and it is assumed that the intermediate stress (σ2) has no influence on the strength of a rock.

Trenchlesspedia explains Mogi-Coulomb Criterion

The Mogi-Coulomb criterion equation takes into account the intermediate stress as well as the intersection of the line axis, represented as Toct and the line inclination.

The strength parameters for both a and b relate to the cohesion and friction angles of triaxial compression and uniaxial compression.

Toct = a + bσm,2

When ignoring the intermediate stress and utilize solely the Mohr-Coulomb criterion, the overall rock strength may be greatly underestimated. Conversely, some believe the Mogi-Coulomb criterion greatly overestimates overall rock strength.

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