Study of Failure Envelope of Soils

The extension of the Mohr-Coulomb failure criterion to the case of three-dimensional stress was studied by triaxial tests on hollow cylindrical specimens with pore-water pressure measurements. The results on clay agree well with the Mohr-Coulomb envelope expressed in terms of the Hvorslev strength parameters and indicate that the strength is independent of the intermediate principal stress. The strength of sand is dependent on the intermediate principal stress. When it is different from the major or minor principal stresses, the value of ∖a/ is higher than that measured in triaxial compression or extension tests. The stresses in the hollow cylinder at failure were analyzed by the theory of plasticity.