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Cranfield University

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Experimental Methods<br />

The cooking pot was filled with soil in the following manner:<br />

2320 g of soil with 9 % moisture content were uniformly crumbled with no soil aggregates<br />

of more than 5 mm diameter remaining. Then 1160 g were weighed into the cooking pot<br />

and afterwards compressed by 15 mm with a 120 mm diameter plate. Afterwards the re-<br />

maining 1160 g of soil were weighed into the pot and the sample was compacted by 15<br />

mm again which left the 120 mm high pot filled to 100 mm. With a volume of 1.615 l (140<br />

mm diameter filled to 105 mm height) and a dry weight of the soil of 2119 g the resulting<br />

DBD was 1.312 g/cm 3 .<br />

Then the plate was placed in the centre of the pot as previously described and the pot was<br />

put into the triaxial cell. The sample was docked and the chosen load application carried<br />

out. Force, time and sinkage measurements were automatically taken by the triaxial appa-<br />

ratus. The force was usually applied to replicate a pressure measurement of the soil bin<br />

from Ansorge (2005, b) as shown in Figure 21 (right) and only for the comparison study of<br />

average to peak pressure (7.4) applied as shown in Figure 21 (left). The average pressure<br />

was the same for both curves. The scales are relative. The Y-axis symbolizes the propor-<br />

tion of the total load applied at any given time within the cycle whereby the relative time<br />

scale is represented by the X-axis. For 0.5 Hz the cycle time is 2 s, thus 1000 corresponds<br />

to 2 s. After the experiment the pot was taken out and the soil removed, crumbled and the<br />

entire procedure repeated again.<br />

Relative Pressure Scale<br />

1,00000<br />

0,90000<br />

0,80000<br />

0,70000<br />

0,60000<br />

0,50000<br />

0,40000<br />

0,30000<br />

0,20000<br />

0,10000<br />

0,00000<br />

0 200 400 600 800 1000<br />

Relative Time Scale<br />

1,00000<br />

0,90000<br />

0,80000<br />

0,70000<br />

0,60000<br />

0,50000<br />

0,40000<br />

0,30000<br />

0,20000<br />

0,10000<br />

0,00000<br />

0 200 400 600 800 1000<br />

Ph.D. Thesis Dirk Ansorge (2007)<br />

Relative Pressure Scale<br />

Relative Time Scale<br />

Figure 21: Left hand side: average pressure; right hand side: peak pressure replicating<br />

true tyre pass data from the soil bin. Both curves are on relative scales<br />

30

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