  A recent model showed how a clay shrinkage curve is step-by-step transformed
into the shrinkage curve of an aggregated soil at any clay content if it is
measured on samples so small that cracks do not occur at shrinkage. Such a
shrinkage curve was called a reference curve. The present work generalizes this
model to any soil sample size or layer thickness, i.e., to any crack
contribution to the shrinkage curve. The approach is based on: (i) recently
suggested features of an intra-aggregate structure; (ii) detailed accounting
for the contributions to the soil volume and water content during shrinkage;
and (iii) new concepts of lacunar factor, crack factor, and critical sample
size. The following input parameters are needed for the prediction: (i) all
parameters determining the basic dependence of the reference shrinkage curve;
(ii) parameters determining the critical sample size (structural porosity and
minimum and maximum aggregate size at maximum swelling); and (iii) initial
sample size or layer thickness. A primary experimental validation of the new
model concepts is conducted using the relevant available data on the shrinkage
curves of four soils with different texture and structure that were obtained
utilizing the samples of two essentially different sizes. The results show
evidence in favor of the model.
