  Physical understanding of the links between soil swelling, texture,
structure, cracking, and sample size is of great interest for the physical
understanding of many processes in the soil-air-water system and for
applications in civil, agricultural, and environmental engineering. The
background of this work is an available chain of interconnected physical
shrinkage curve models for clay, intra-aggregate matrix, aggregated soil
without cracks, and soil with cracks. The objective of the work is to
generalize these models to the case of swelling, and to construct the
physical-swelling-model chain with a step-by-step transition from clay to
aggregated soil with cracks. The generalization is based on thorough accounting
for the analogies and differences between shrinkage and swelling and the
corresponding use, modification, or replacement of the soil shrinkage features.
Two specific soil swelling features to be used are: (i) air entrapping in pores
of the contributing clay; and (ii) aggregate destruction with the formation of
new aggregate surfaces. The input for the prediction of the swelling curve of
an aggregated soil coincides with that of the available model of the shrinkage
curve. The analysis of available data on the maximum shrink-swell cycle of two
soils with different texture and structure, accounting for sample size is
conducted as applied to swelling curves and to the residual crack volume and
maximum-swelling-volume decrease after the shrink-swell cycle. Results of the
analysis show evidence in favor of the swelling model chain.
