Cranfield University

Soil Compaction Models
sibilities to obtain the mechanical parameters of the soil, and 4) derive a conclusion from
literature.
6.1.1 Theoretical Background of Soil Compaction Models
Preliminary soil compaction models can be divided into empirical models and soil mechan-
ics models. The available soil mechanics models describe qualitatively the true impact of
different treatments on soil compaction. However, quantitatively they fit best the data they
were originally generated for. Reasons for this are the influence of organic matter, soil
moisture content, soil type, and physical soil structure on both pressure transmission within
the soil and on soil compactability.
At a first glance these facts increase the attractiveness of empirical models. However, to
generate an empirical model one has to use large amounts of input data in order to make it
reliable and applicable in a range of situations. The second drawback is the fact that it con-
tributes little to the fundamental understanding of soil physical behavior and soil physical
laws.
Soil mechanics models are usually a combination of soil mechanical principles and nu-
merical techniques. Most models use either a finite element analysis or some approach
which can be categorized into elastic theory and minor extensions of it. The advantage of
taking the elastic theory approach is that it is a simple route for improvement and cannot
only predict stress, but predict both stress and strain using Young’s Modulus and Poisson’s
Ratio. A slightly different approach based on the elastic theory is the critical state soil me-
chanics which aims on describing volumetric soil response in regard to soil hydrostatic and
shear stress. This was implemented by both Schofield and Wroth (1968) and Kurtay and
Reece (1970). A detailed description of elastic soil modeling is given by Wulfsohn and
Adams (2002). The authors describe the basics beginning with a purely elastic behavior
following Hooke’s law (which was utilized by Soehne, 1953 and all approaches based on
his work) and finishing with a detailed explanation of Critical State Soil Mechanics. On the
contrary FEA models are difficult because they require many empirically determined input
parameters. Critical state soil mechanics theory was initially developed for saturated clay
soils, and later used to explain behavior of agricultural soils for example by Spoor and
Godwin (1979). Towner (1983) describes the stress state in partially saturated soils with
Ph.D. Thesis Dirk Ansorge (2007)
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