A study on theories of plasticity and their applicability to soils under environmental factors

Abstract

A review of the types of rate independent theories for soils is given, together with a more detailed newlinesurvey of plasticity theories. The contributions of particulate mechanics are briefly summarized. The newlineremainder of the dissertation is divided into two parts, dealing respectively with a theoretical and newlineexperimental study of the applicability of plasticity theory to soils. Some additional information is newlinegiven in Appendices. Part I begins with some theoretical preliminaries. Kinematic variables and their newlineconjugate forces, internal variables and the theoretical restrictions on plasticity theory are introduced. newlineThe need for a less restrictive approach is explained, and this is met by a thermo mechanical newlineformulation of plasticity theory. Some implications of the theory and some specific examples are newlinegiven, including models involving non-associated flow and the principle of effective stress. A detailed newlinediscussion of the derivation of the Modified Cam-Clay model from the thermo mechanical method is newlinegiven, including comparisons with earlier energy theories for clays. The model is extended to general newlinestress states and to largestrain theory. Some modifications of the model are then considered, including newlinechanges to the yield locus and a study ofa shear modulus dependent on pressure or reconsolidation newlinepressure. Experimental data on the variation of the shear modulus cue discussed. Part I concludes with newlinetwo aspects of soil behavior not yet included in the thermo mechanical Approach the generalization of newlineyield loci in the octahedral plane and the development of anisotropy. The material for experimental newlinestudy is described, and the types offertory the applicability of plasticity theory discussed. An newlineinvestigation of the effect of stress and of stress history on a dense sand in triaxle compression, using a newlineprogram of stress cycle tests newline