Plane Strain Formulation for Elastic-Plastic Behavior

The finite element technique has a high level of sophistication and versatility and further progress in expanding analytical capabilities in soil mechanics depends upon a consistent mathematical formulation of general and realistic constitutive relationships. Until the present time proposed formulations used in numerical analyses have been mainly on an incremental use of elasticity theory. Experimentally it is observed that: 1. Many soils are inelastically deformed almost immediately upon application of stress; 2. there is a coupling between volume changes and changes in shear stress; 3. the deformations are stress path dependent; 4. dense soils expand in volume during pore shear; and 5. many soils, drained or undrained, experience a decrease in strength with further straining after a peak strength has been reached.