Analyzing grain size distributions with the modal decomposition method: potential for future research in engineering geology

摘要

Many studies describe soils by their grain/particle size distribution (GSD/PSD). Most samples are poly-disperse collections of solids. A companion article has reviewed earlier methods to fit a GSD: usually, their R-2 value is in the 0.5-0.9 range. A modal decomposition method, MDM, was developed to extract from a GSD its sub-populations or modes, proportions, and specific surface area. This new MDM is easy to use in a spreadsheet and yields a R-2 value typically over 0.999. This article explores the MDM potential for future research in engineering geology. Examples are provided for the accurate mathematical description of the GSD, instead of using a few parameters and adjectives. For stratified formations, the MDM found that their sub-layers respect the usual filter criteria for well-graded or 1-mode soils. For internal erosion, the MDM has made it clear that the usual criteria are not enough and two new criteria seem to be needed, about the d-length over which the GSD slope criterion is not respected and its position. These new results should interest many researchers. In short, the MDM appears as a promising and useful tool for future research in engineering geology because it gives a close-to-perfect fit for the GSD, has the capacity to better define quantitatively a GSD, the capacity to better understand and define the conditions for filtering actions, and for the risk of internal erosion.