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|Document Type: ||Thesis or dissertation|
|Title: ||Soil reaction to heavily loaded rubber tracks and tyres|
|Authors: ||Ansorge, Dirk|
|Supervisors: ||Godwin, R. J.|
|Issue Date: ||12-Oct-2007|
|Abstract: ||The importance of undercarriage design with respect to its effect on soil density changes
grows with the size of harvest machinery. Therefore this study elucidates the mechanics of
soil displacement caused by different undercarriage systems of combine harvesters on soil.
The soil displacement caused by different undercarriage systems at maximum working
weight was measured by embedding tracers into the soil in both the soil bin laboratory and
the field studies. The effects of different tyres, tracks, and whole undercarriage systems on
soil density increase were significant. The results from whole machine systems were validated
with field experiments using fish-hooks for measuring displacement on a sandy loam
and a clay soil. The draught force of a tine loosening the soil after the passage of whole
machines was also investigated.
With an increase in speed, soil density increase was reduced. The implement tyre evaluation
emphasized the importance of tyre width, diameter, and inflation pressure on soil density
increase. The evaluation of whole machine systems showed that the influence of rear
tyre size on additional soil density increase is larger for wheeled than for tracked undercarriage
systems. The strong layer at the surface from a track is able to carry the rear tyre
without further compaction of the soil below leading to an overall soil displacement similar
to a wheeled machine of 1/3 of the weight. The evaluation of different track systems emphasized
the effect of the number of rollers on soil physical parameters. Variations in a
high belt tension range showed only small effects.
A novel approach was developed determining virgin compression line parameters in-situ
from contact pressure, rut and working depth enabling an easy adjustment of a model to
given soil conditions and a successful prediction of soil displacement for tyres. The in-situ
approach can be used for tracks, but a different VCL results. The in-situ VCL was validated
with small scale plate sinkage tests and compared to results from triaxial cell testing.
Results from triaxial tests showed that the VCL depends on the relation of major and minor
principel stresses. Ancillary experiments were carried out to shed light on longitudinal soil
movement and the influence of lugs and pressure history on soil displacement. In addition
a new heuristic model involving load per perimeter length was tested and the “punching
failure” of soil observed justified with theories from literature. Ancillary experiments showed that the dense layer at the surface from the tracks originates
from a backward soil movement limited to the uppermost 150 mm. The lug influence of
both tyres and tracks was insignificant from 200 mm depth downwards. From heuristical
data analysis the load per perimeter length was identified as an important variable. Peaked
pressure history caused about 1/3 more sinkage than constant contact pressures.|
|Appears in Collections:||PhD, EngD and MSc by research theses (School of Applied Sciences)|
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