A new normalisation scheme for normal compression and critical state line for soils

Abstract

Unlike clays, sands may exist in a virgin condition, but at different initial void ratios. Therefore, there is no consensus in the literature as to the definition of the normal compression line for sands. On the basis of experimental evidence, this paper presents a new simple normalisation scheme to unify the compression response of sands. The normalisation scheme incorporates both the initial void ratio and its corresponding equivalent stress on the limiting compression line as normalising parameters. The novelty of the new normalisation scheme is that it is not only consistent with the framework of critical state soil mechanics, but it is also conceptually in line with recent studies on crushability of soils. The validity of the new normalisation scheme is verified against a wide range of experimental data from isotropic and 1-D compression tests on both sands and clays. It is also shown that a unified compression relationship can be obtained for both clays and sands by taking into account the differences in the compression index at high pressure. Similarities between the compression curves and the critical state line for different soils are also examined, and it is shown that the critical state line for clays and sands can be uniquely represented using the proposed normalisation scheme. Areas for further research, where the new normalisation scheme is deemed valuable, are highlighted.