An integrated approach to soil structure, shrinkage, and cracking in samples and layers

摘要

A recent model showed how a clay shrinkage curve is step-by-step transformedinto the shrinkage curve of an aggregated soil at any clay content if it ismeasured on samples so small that cracks do not occur at shrinkage. Such ashrinkage curve was called a reference curve. The present work generalizes thismodel to any soil sample size or layer thickness, i.e., to any crackcontribution to the shrinkage curve. The approach is based on: (i) recentlysuggested features of an intra-aggregate structure; (ii) detailed accountingfor the contributions to the soil volume and water content during shrinkage;and (iii) new concepts of lacunar factor, crack factor, and critical samplesize. The following input parameters are needed for the prediction: (i) allparameters determining the basic dependence of the reference shrinkage curve;(ii) parameters determining the critical sample size (structural porosity andminimum and maximum aggregate size at maximum swelling); and (iii) initialsample size or layer thickness. A primary experimental validation of the newmodel concepts is conducted using the relevant available data on the shrinkagecurves of four soils with different texture and structure that were obtainedutilizing the samples of two essentially different sizes. The results showevidence in favor of the model.