A Simple strain-space plasticity model for clays

Abstract

This thesis develops and demonstrates a simple strain-space constitutive model for wet clays. It has been seen that a strain-space formulation of the constitutive behavior of engineering materials facilitates the solution of boundary value problems involving these materials. Soil, because of its multi-phase granular constitution poses challenging problems in constitutive modeling. Although several stress-space plasticity models exist for soils. they are not used commonly in engineering practice due to their complexity. It is attempted herein to develop and test a simple model which could result in simplified solutions for some soil problems. The model is based on the experimentally observed physical behavior of soil. Certain approaches alien to conventional plasticity, are employed so that the material behavior is closely predicted without sacrificing the simplicity of the model. The model is initially developed for triaxial load systems. Its predictions are then tested against other model predictions and experimental data. The model is then generalized. The generalization renders the model capable of handling general stress-strain states and finite deformations. Finally, the generalized model is used to solve an idealization of a practical problem. The problem of a pile driven into a soil medium is idealized as an expanding cavity in a homogeneous infinite medium. The solution predicted by the strain-space model is compared with other model predictions and test results.