Imperfection sensitive strength variation of soil specimens

The mechanism of the statistical variation of the shearing behavior of soil specimens is investigated from the viewpoint of bifurcation, under the major assumption that these specimens undergo elastic bifurcation, and that such variation is ascribed to the variation of initial imperfections among specimens. Through a synthesis and an extension of the pre-existing bifurcation theory, we advance a method to describe that variation. Two series of triaxial compression tests are conducted to construct a data bank of the shearing behavior of sand specimens. An imperfection sensitivity law is employed to describe the variation in their axial strain versus axial stress curves and volumetric strain versus axial stress curves, and hence to assess the validity of those assumptions to demonstrate the predominant role of elastic bifurcation in soil shearing behavior. The theory of the stochasticity of initial imperfections is employed to explain the probabilistic variation of the maximum strength.