Abstract:
A prediction model
based
upon Mohr-Coulomb soil
mechanics
theory has been developed to predict the
interaction between the
soil and agricultural
discs
of
different
geometries and operating angles to both
vertical
and tilted discs. The model
is based
on two forms
of soil
failure. The magnitude of each
form
of
failure is depen-
dent
upon a passive reaction on the concave side of the
disc
and a vertical
bearing
reaction on the convex side
of the disc. The predicted results are
in
close agreement
with
the results of the experimental studies.
Disc geometry
is
one of the
most
important factors
to be
considered
in
evaluating the soil reaction acting
upon a
disc tool. A theoretical
analysis of the disc
geometry was
therefore carried out. The analysis of
the disc geometry makes
it
possible to determine the
factors required
for the predicted
forces
acting on a
disc tool.
The experimental studies were conducted
in a sandy
loam
soil at a moisture content
in the friable
range, under
controlled soil
bin
conditions. The
work was carried out
at
full-scale with
3 dimensional force
measuring apparatus
developed primarily
for this investigation. The discs
studied
had a range of
disc
angles
between 150 and
600
and a range of tilt angles between 0
and
35. The depth
of cut ranged
from 80
mm to 140
mm and at speeds
between 0.75 m/s and
1.5
m/s.
The disturbance
area of the soil caused
by the
rotating soil cutting
disc is
calculated to define the
disturbed
area
for
any combination of
disc
angle,
disc
diameter, gang spacing and
depth
of work
in order to
accurately calculate specific resistance.
Disturbance and soil
inversion
were
investigated
using transparent discs
and soil tracers, with a variety
disc
and
tilt angles
in
order to quantify
inversion
and mixing.
