Cranfield University

Appendix
Appendix 1 Further Details on Soil Compaction Models
Appendix 1 contains additional detailed information concerning Sections 6.2 throughout to
6.8. Consequently, some of the figures given in the thesis sections will be repeated in the
Appendix allowing the reader to easily follow the argumentation
11.1.1 Comparison of Soil Compaction Models
The variety of approaches used to model and indicate soil compaction rose the question how
it would be possible to compare them directly, ideally comparing the same parameters. Most
soil compaction models give different final outputs ranging from final real DBD (O’Sullivan,
1998) over the prediction of an area of excess of soil stability (van den Akker,
2004/SOCOMO) to just a danger of soil compaction (Etienne and Steinmann, 2002/TASC).
Their common basis is the calculated stress propagation in the soil leading to the final
prediction of soil compaction. Thus comparing their performance in stress prediction to
measured soil stresses in the soil bin can determine the accuracy of the stress prediction of the
models. Therefore this section contains a comparison of soil compaction models with respect
to pressure prediction and a sensitivity analysis of COMPSOIL and SOCOMO.
11.1.1.1 Comparison of Pressure Prediction
The vertical stress propagation predicted by SOCOMO, COMPSOIL, and TASC will be
compared in this section.
During the project conducted by Ansorge (2005) in the soil bin soil stresses were also
determined. The vehicle support mechanics were both the rubber track and the 800 mm
section width tyre laden to different values and inflation pressures. The pressure in the soil
below the treatments was measured using ceramic pressure transducers embedded on
aluminum tubes as described in Ansorge (2005). The pressure was measured at depths of 250
mm, 400 mm, and 650 mm. As the ceramic pressure transducers were embedded into the soil
parallel to the surface the pressure measured is the vertical normal stress component. All three
models (TASC, SOCOMO and COMPSOIL) give vertical normal stress values at the
measured depths. The model by O’Sullivan however, can not predict the stresses deeper than
475 mm. In consequence of this limit the O’Sullivan model was excluded from the
Ph.D. Thesis Dirk Ansorge (2007)
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