Cranfield University

Appendix
The results from above agree to a certain extend with the expected results. A larger soil
displacement and therefore increase in soil density is expected with a weaker soil. In
consequence of the weaker soil conditions the increase in soil failure is appropriate, which
was indicated by the different letters. However, the expected reduction in soil compaction
with an increase in preconsolidation stress could not be shown using the model.
Figure 3: Estimated combined failure area for 680/10.5/2.2 at a preconsolidation
stress of 200 kPa (P = excess of preconsolidation stress)
Figure 4: Estimated combined failure area for 680/10.5/2.2 at a preconsolidation
11.1.1.2.2 COMPSOIL
stress of 100 kPa (P = excess of preconsolidation stress, S = excess of shear strength, C = excess of both)
As the original spreadsheet embedded in COMPSOIL was locked, soil critical state
parameters could not be changed directly in the O’Sullivan model, therefore only soil density
and soil water content were changed. Soil water content and dry bulk density with
corresponding outputs of the model are shown in Table 3. The discussion and explanation of
the changed parameter and results follow after the table.
Firstly, the contact area of a track can be mimicked by a 2 m wide and 1.2 m diameter tyre,
yet it is not possible to assess the implications on soil mechanical properties in the model as in
reality the contact area is turned by 90 degrees. The influence of contact shape was calculated
Ph.D. Thesis Dirk Ansorge (2007)
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