Cranfield University

Appendix
taken into account soil displacement is totally overestimated. With only cell volume (VCL
A+R Cell Quickly) change the approach is closer to the prediction with the tyres, however,
underestimates the resulting sinkage.
If the axial load is applied slowly by a constant strain rate and only cell volume change is
taken into consideration “VCL A+R Cell Slow” shows the correct shape and underestimates
total displacement less than “VCL A+R Cell Quickly ” did. If in the slow case height change
is taken into consideration, too, “VCL A+R Cell+Height Slow” shows a closer agreement at
the surface, but the entire shape of the curve changed making it less appropriate.
Depth (mm)
0
100
200
300
400
500
600
700
800
Displacement (mm)
0 50 100 150 200 250 300 350 400
Measured 900/10.5/1.9 Soil Bin VCL w ith Conc=5
Soil Bin VCL w ith Mean Norm= Contact Pressure VCL only SphericalPressure (2nd Day 1st VCL)
VCL A+R Cell+Height Slow VCL A+R Cell+Height Quickly
VCL A+R Cell Slow VCL A+R Cell Quick
Figure 39: Different ways of gaining VCL to describe 900/10.5/1.9 treatment
The following figure will compare the average VCLs gained in the previous section to both,
the unique “VCL A+R Cell Slow” from the previous diagram and the initial soil data. Using
the VCL parameters gained from “VCL Average Dense” soil displacement is overestimated at
depth, although in the top 150 mm it agrees most closely to the measured soil movement. The
prediction of soil displacement for “VCL Average 5” agrees with the “VCL A+R Cell Slow”
which shows that this VCL created initially “randomly” without replications is in fact not
random. As discussed before soil displacement for these two lines is overestimated at depth
and underestimated at the surface. Pre-selecting the 3 from the 5 VCLs to gain an average
actually lead to an even larger error between measured and predicted soil displacement.
Ph.D. Thesis Dirk Ansorge (2007)
231