Normalisation Techniques for Slowly-converging Soils

The existence of a unique normal compression, NCL, and critical state line, CSL, for clean sands and clays in the state plane, v-lnp', is generally assumed. Recently, some soils of either complex grading or mixed mineralogy did not exhibit this convergent type of behaviour in the state plane at typical stress and strain levels. This investigation proposes different normalisation techniques for non-convergent soil mixtures consisting of fractally-graded single mineral sands, either quartz or calcium carbonate, with very large amounts of non-plastic fines. For the mixtures, the typical normalisation techniques do not work because a straight NCL, parallel to the CSL, could be defined only in the region of very low specific volumes and extremely high stress levels. Similarly, a normalisation based on an equivalent pressure p'e,CSL taken on a unique straight CSL could not be applied because of the existence of curved and multiple CSLs.