ANALYTICAL AND EXPERIMENTAL CHARACTERIZATION OF STRESS INDUCED ANISOTROPY IN A WEAK AND SOFT SOIL (PRINCIPAL, ROTATION)

Little information is presently available with regard to the constitutive behavior of anisotropic soils. Engineers face two principal difficulties when solving practical problems, i.e., realistically develop constitutive equations for anisotropic soil and how to measure experimentally soil responses under complex loading conditions.; The primary objective of this study was to develop a new laboratory experimental technique and device which can realistically simulate the in-situ stress condition, and conduct the laboratory experiments to study the behavior of stress induced anisotropic soil, utilizing the developed technique and device. The secondary objective was to search for an analytical formulation that could be incorporated in the constitutive equations such that it could be properly devised to solved engineering problems.; The new Directional Shear Cell (DSC) has been developed at the Department of Civil, Environmental and Architectural Engineering of the University of Colorado, Boulder. The DSC has shown to be a reliable tool to investigate the behavior of anisotropic soil in the laboratory. The artificial soil used in this investigation was very weak and soft. The experimental evidence shows that the magnitudes of major and minor principal stresses which induced the anisotropy to the specimen affect the reloading stress-strain responses of the specimen. The stiffness of the induced anisotropic soil changes with the direction of the re-applied principal stress. In general, when the angle of the principal stress rotation increases, the stiffness of the specimen decreases.; The incorporation of the relationship between principal stress directions and the material principal axes in the Bounding Surface constitutive model has a very promising results in simulating the laboratory results.