Macro–micro measurement of particle arrangement in sheared kaolinitic matrices

Two series of shear tests on normally consolidated drained and over-consolidated drained kaolinitic test specimens were performed in a triaxial cell coupled with petrographic investigations. The axial deformation, the volumetric deformation and the void ratio changes were measured during each shear test in order to represent the macroscopic behaviour of the material in the Cam Clay diagram. The macroscopic-to-microscopic relation was treated through microscopical analysis of thin sections under polarised light coupled with image analysis and grey-level diagram analysis in particular. The image analysis quantifies the percentage increase of the parallel orientated particles from the sub-isotropic matrix of the initial consolidated sample to the quite anisotropic matrix of the normally consolidated sheared samples. The SEM observations indicate particle movements that allow the measurement of the void ratio differences between the matrix and the shear planes by microprobe analysis.