Constitutive equations for pressure-sensitive soils: theory, numerical implementation, and examples

Soil consists of an assemblage of particles with different sizes and shapes which form a skeleton whose voids are filled with various fluids. The stresses carried by the soil skeleton are conventionally termed ‘effective stresses’ in the soil mechanics literature, and those in the fluids are called ‘pore-fluid pressures’. The soil’s anisotropy originally develops during its deposition and subsequent consolidation which, in most practical cases, occurs under no lateral deformations. The model parameters required to characterize the behaviour of any given soil can then be derived entirely from the results of conventional monotonic axial and cyclic strain-controlled simple shear soil texts. The smooth experimental stress-strain curves obtained in axial tests are approximated by linear segments along which the tangent modulus is constant. Predictions about the constitutive behaviour of the soil subjected to loading stress paths not identified in the data had been requested by the organizing committee.