Calibration of 3-D Failure Criteria for Soils Using Plane Strain Shear Strength Data

Design of many geotechnical problems, such as the stability of slopes and excavations, are strongly governed by the shear strength of soil represented in three dimensions. In literature, a number of failure criteria have been proposed using isotropic invariant of stress tensor in three dimensional stress spaces. For a linearly pressure-dependent material, there are four basic failure criteria which have been commonly used to describe the behavior; Mohr-coulomb, Drucker—Prager (1952), Lade and Duncan (1975), and Matsuoka and Nakai (1985). Mohr-Coulomb criterion is defined in a 2-D stress space and it follows plane strain condition. The other three which are 3-D failure criteria have been considered during this study for analysis. Calibration of such a model is relatively easy when the tests are performed in axisymmetric conditions and principal stresses are applied on the specimen, e.g. triaxial tests. This paper will present the solutions for calibrating such failure criteria assuming associative flow rule and using the shear strength parameter (φ_ps) obtained from the laboratory tests performed under plane strain conditions e.g. Direct Shear and Simple Shear Test.