Folie 1

1
Soil stress due to high wheel loads M.
Konstantinovic, P. Schulze Lammers, L. Damerow
INTRODUCTION The wheel-traffic necessary for
most farm operations is a major cause of soil
compaction. In contemporary design, there is a
trend towards larger machines because such are
expected to have higher degrees of efficiency.
Although this trend results in higher axle loads,
tire-soil contact areas are not growing at a
commensurate pace. The result is that contact
pressures and soil stresses are increasing.
Therefore, tests were conducted with a large
1050/50 R 32 tire not only to measure the
foot-print area but also to evaluate the pressure
under the tire.
The foot-print area of the tire lugs was measured
by digital photo analysis. The pressure was
averaged according to Fig. 2 because there was no
information about the pressure distribution in
the foot-print.
Tab. 1 Testing conditions for foot-print
area determination stand
Fig. 3 Test results, contact pressure and
contact area
Foot-print of thetire 1050/50 R 32
Fig. 4 Soil Layer Method
- proposed for measuring stress
in the soil
Fig. 1 Test stand for foot-print area
determination
DISCUSSION CONCLUSION Since the information on
the pressure from Fig. 3 represents only average
pressure on the soil surface, it is necessary to
acquire in-soil values of stress and stress
distribution. Therefore a Soil Layer Method
using area sensors was developed and pre-tested
using stamps. According to the pre-tests, it is
concluded that the pressure-sensitive film used
could not be calibrated to the required levels of
accuracy. A general conclusion of the pre-tests
is that this method, if improved, may have a
potential to yield useful information on soil
stresses under the soil.
Fig. 2 Approximation of pressure by using the
average pressure value, PmeanF/Alugs
Institut für Landtechnik, Nußallee 5, 53115
Bonn Tel. [phone], Fax 0228/73
2596 www.landtechnik.uni-bonn.de