Cranfield University
Cranfield University
Cranfield University
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Ancillary Experiments<br />
� A developed peak in penetrometer resistance can protect the subsoil and further<br />
compact vertically as shown with the rear tyres following a track thereby increasing<br />
its peak and possibly vertical compaction, yet the origin of an increase in peak<br />
penetrometer resistance can only be detected by looking at soil displacement and<br />
penetrometer resistance curves.<br />
7.2 Influence of Lugs on Soil Displacement with Depth<br />
Looking at the field surface after the passage of a tyre/track, the imprint of the lugs is very<br />
pronounced and challenges the question how deeply the lugs affect soil density increase.<br />
Information concerning the influence of lugs and inter lug area on soil compaction is lim-<br />
ited. Whenever soil pressure was measured a difference in lugged and non lugged area<br />
could be detected (Gupta and Raper, 1994). As the authors stated the differences were not<br />
accounted for and it is difficult to account for them as their effect reduces with soil depth.<br />
Rusanov (1997) developed equations to calculate the pressure exerted by lugs on the soil at<br />
the tyre-soil interface. Way et al. (1993) found contradicting results with respect to soil<br />
density influenced by different lug heights on the same type of tyres and pressure peaks<br />
could only be found in a depth range of 160 – 280 mm (after removing outliers). The depth<br />
to which soil displacement was actually influenced by lugs had not been investigated. To<br />
shed light on this question photographs and diagrams from the talcum powder traces in the<br />
soil bin were analyzed.<br />
When studying a soil profile after the passage of a wheel on relatively weak uniform soil<br />
condition, with an initial DBD of approximately 1.38 g/cc, lug displacement was visible to<br />
a depth of approximately 100 - 200 mm in Figure 102. This depth of lug influence was<br />
similar for all treatments.<br />
The effect of the influence of the lugs on soil displacement is also shown in Figure 103<br />
which represents a digital picture of the soil displacement in Figure 102. It shows the small<br />
heap on the right hand side of the centre in the third line from top, however, below this<br />
depth of 100 mm there was no further indication of lug influence.<br />
Ph.D. Thesis Dirk Ansorge (2007)<br />
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