The influence of the first invariant of the effective stress tensor upon the deviatoric response of a cohesive soil is investigated. Triaxial compression tests with effective octahedral normal stress control show the deviatoric stress-strain response to be definitely affected by the value of the effective octahedral stress,. The values ofrange from 7.5 psi to 30.0 psi. For a constant value of strain, the deviatoric stress increases with an increase in. The ultimate shear strength can be approximated as a linear function of. Hyperbolic representation of the stress-strain response provides a convenient method for obtaining a measure of the ultimate shear strength using the response of stress states other than failure. The deviatoric stress-strain response as a function of the effective octahedral stress,, can be expressed in the normalized formwhere ε is the strain,is a measure of the shear strength expressed in terms of, andAas well asBare numerical coefficients