Cranfield University

Ancillary Experiments
7.1.2 Longitudinal soil displacement
The plastic longitudinal soil movement was measured by placing a series of 5 mm diameter
vertical columns of sand into the soil at a spacing of 50 mm to a depth of 250 mm in the
centreline of the path of the tyre or track. After the passage of the tyre/track these were
carefully excavated along the centre line. The position of each sand column was digitized
using the same methodology as for the talcum powder lines. Figure 99 shows a uniform
forward soil movement after the passage of the 900/10.5/1.9. To aid the interpretation of
soil movement within the column, Figure 99 includes vertical lines representing the aver-
age longitudinal position of the lower 100 mm for each sand column. The forward move-
ment varied depending on the position relative to the lug. The columns on the back of a lug
exhibited only a forward movement close to the surface, but not at depth (Column 1, 6, and
10 from left); all other columns tilted forward. The soil movement caused by a rubber track
at 12 t is shown in Figure 100; these show an alternating backward and forward soil
movement, whereby the backward movement was more pronounced than the forward
movement. The front face of a lug appears to push the soil slightly forwards (Columns 2, 5,
and 8 from left), but the remaining section of the lug and the rear area push the soil back-
wards. The lug-void ratios in these particular cross sections were 0.43 for the track and 1
for the tyre, representing a larger proportion of lugs for the tyre within the contact area.
Depth, mm
0
50
100
150
200
250
300
350
400
Length, mm
800 900 1000 1100 1200 1300 1400
1 2 3 4 5 6 7 8 9 10
Figure 99: A digital image of the longitudinal position of the sand columns after the
passage of a 900/10.5/1.9 tyre
Ph.D. Thesis Dirk Ansorge (2007)
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