Impacts on geotechnical engineering of several recent findings from laboratory stress-strain tests on geomaterials.doc

Impacts on Geotechnical Engineering of Several Recent Findings from Laboratory Stress-Strain Tests on Geomaterials
F. Tatsuoka
University of Tokyo
ABSTRACT: Significant impacts on the theories and practice of geotechnical engineering of several findings obtained from recent advanced laboratory stress-strain tests on a wide variety of geomaterials that were performed mainly by the author and his colleagues are demonstrated and illustrated. The laboratory stress-strain tests were performed to apply their results to theoretical research as well as practical design. This paper discusses on: 1) elastic properties at very small strains as well as non-linear pre-failure stress-strain behaviour of geomaterials; 2) inherent anisotropy in the strength and deformation characteristics of granular materials; 3) strain localization with shear banding in granular materials; and 4) viscous deformation properties of geomaterials. The importance of knowing the limitations of using over-simplified stress-strain models, such as isotropic linear or perfectly-plastic models, of geomaterials is emphasized. It is attempted to show the important and essential roles of relevant laboratory stress-strain tests of geomaterials in developing the theories and practice of geotechnical engineering. This paper is the lecture note for the 2000 Burmister Lecture, 31st, October 2000, the Columbia University, ., .
INTRODUCTION
Laboratory stress-strain test is only one of the important measures of geotechnical engineering research and practice. In addition, as it is usually very difficult to retrieve sufficiently high-quality undisturbed samples of field geomaterial, it is often considered that the laboratory stress-strain test is less direct (so less useful) pared with the field-loading test. It is particularly the case with ordinary construction projects, in which sophisticated laboratory soil tests may be considered unwarranted, unlike a limited number of huge scale projects. Although it