An anisotropic and time-dependent bounding surface model for clays and its application to a containment system constructed over a soft foundation.

摘要

The main objective of this research is to develop a constitutive model for clays that can simulate realistically the laboratory and field observations of phenomena such as anisotropy, overconsolidation and time dependency.; As the first step of developing a unified model for clays, an Anisotropic Rate-Independent Bounding Surface Model for Clays is presented. The proposed theory is developed within the framework of rate-independent bounding surface soil plasticity and anisotropic critical state concept. The isotropic and rotational hardening rules were adopted. An additional shape (or distortional) hardening rule was introduced in this anisotropic theory to better simulate the anisotropic stress-strain response of clays. The model was compared with the experimental results for three different types of clay: Kaolin, San Francisco Bay Mud and Boston Blue Clay. The comparisons showed that the model is capable of simulating realistically the behavior of isotropic/anisotropic, normally/overconsolidated clays using a single set of parameters.; The proposed anisotropic time-independent theory was incorporated into the Dafalias-Kaliakin model, which is based on the bounding surface plasticity and the Perzyna viscoplasticity. A unified constitutive model for clays is thereby developed. The model predictive capabilities were examined by comparing with the laboratory test results of San Francisco Bay Mud. The results of this comparison are satisfactory.; The proposed time-independent model was incorporated into a two-dimensional finite element program for coupled stress-flow analysis. A containment dike constructed over soft clay foundation was selected as a case study to verify the proposed model. A set of comprehensive field instrumentation results was compared to the results of analysis. The results showed that the agreement between the model and actual measurements is satisfactory. The importance of anisotropy is depicted from the results of this analysis.