Bifurcation as sources of uncertainty in soil shearing behavior

This paper identifies bifurcation phenomena as a major source of uncertainty in soil shearing behavior. On the basis of the bifurcation mechanism, this source is classified into three independent categories: (1) the size effect, (2) the mode change (switching), and (3) the stochasticity of initial imperfections. The size effect is explained considering both fracture and bifurcation, based on tests on rock and soil, and the analysis of a beam on a nonlinear foundation. The mechanism of the mode change, which denotes the variation of the buckling mode due to initial imperfections, for the harmonic and localized bifurcation modes is explained based on the bifurcation behavior of a shell, an atomic chain, and soil. As an essential part of this paper, the theory of the stochasticity of initial imperfections is used to explain the probabilistic variation of the behavior of 32 sets of data for triaxial compression tests on sand specimens. The study of those sources of uncertainty permits a global view of bifurcation, which is vital to the proper understanding of soil behavior.