土質材料における降伏曲線形状と変形挙動の関連

Abstract

Soil has the characteristics of volume change accompanying with plastic deformation, differing from metal. Hence, the equivalent deviatoric stress q at yielding depends on pressure p. The dependency of p on p is referred to as yield curve or yield function. In soil mechanics Cam-clay model and cap model have been frequently used as yield curve. However, it does not seem to have been examined whether the shapes of these yield curves are consistent with the soil behaviour observed experimentally. So far several experiments have been carried out in compressing a parallel piped specimen under plane strain condition for obtaining the information on the onset of shear banding. For predicting yield curve by referring to their results, the following assumptions are set up. Yield curves expand similarlyin shape with plastic de formation and yield function plays as plastic potential. Yield curve prediction needs two kinds of physical values measured in tri-axial compression tests, for example axial stress, volumetric strain and so on. Under a certain condition the yield curves predicted have the similar shapeto that in Cam-clay model. In these procedures modified hardening characteristics were used, and it was found that the characteristics also are very similar to that in Cam-clay model.