UBC Theses and Dissertations
A critical assessment of a constitutive theory for soils Wong, Colin L. Y.
A constitutive theory for soil proposed by J.H. Prevost is explained in detail and examined for its limitations, appropriateness of assumptions, and capabilities. Three models using this theory are appraised: an undrained total stress formulation, an effective stress model for cohesionless soil, and a general effective stress model for any type of soil. The necessary equations are derived and the consequences of the implicit assumptions discussed. Methods for determining the parameters are presented and comparisons of the model predictions with actual test data are also made. It was found that the undrained total stress model is remarkably accurate for predicting the behavior of a kaolinite clay under a complex monotonic stress path. However, caution must be exercised when applying the model to heavily overconsolidated clays. Problems may also be encountered when applying the model to strain softening soils subjected to complex load paths. The effective stress models do not give good comparisons between predictions and test data. Some of the problems include a restriction of the models to monotonic loading and a mathematical inconsistency in formulating the general effective stress model. In their present form, the effective stress models are not suitable for predicting the effective stress behavior of soils.