The time- and temperature-related behavior of clays: Microscopic considerations and macroscopic modeling

Abstract

The prediction of stresses, deformations and temperature as a function of time in a material subjected to simultaneous thermal and mechanical loading is one of the most challenging and complex problems in engineering mechanics. In the field of Geomechanics a number of important problems exist that necessitate the realistic prediction of time-dependent thermal-mechanical behavior. Thermal-mechanical analyses of soils are complicated by the nature of these materials. Soils consist of a porous skeleton whose voids are filled with fluid and gas. Consequently, soils are nonhomogeneous materials. Macroscopically such materials exhibit an anisotropic, inelastic, path-dependent, strain hardening (and softening), time-, rate- and temperaturedependent behavior. To further complicate matters, the thermal properties of such materials are not as well known as those for othermaterials such as metals. The variability in a soil's composition and subsequent degrees of thermal and mechanical dependency further increase the complexity of the thermo-mechanical behavior of such material. Finally, natural soils are also subject to sample disturbance that makes the task of representative testing all the more difficult. Local variations in soil composition often preclude the obtaining of reproducible test results, and thus impose limitations on the confidence associated with the analytical description of the soil behavior. This chapter briefly discusses the rudimentary microscopic and physicochemical aspects associated with saturated cohesive soils. This is followed by a discussion of the macroscopically observed time- and temperature-dependent behavior of such soils. Finally, a combined and coupled thermo-elastoplastic-viscoplastic framework for modeling the anisotropic, time-, rate- and temperature-dependent behavior of cohesive soils in the context of a bounding surface formulation is proposed. © 2014 Nova Science Publishers, Inc. All rights reserved.