The Delft Sand, Clay & Rock Cutting Model, 2019a

Saturated Sand Cutting.
side effects is researched by measuring the forces on both the middle blade as on the side blades. Possible present
transversal forces are researched by omitting one side blade in order to be able to research the transversal forces
due to the three-dimensional side effects. For this research the following blade configurations are used:
1. A middle blade of 150 mm and two side blades of 185 mm each.
2. A middle blade of 200 mm and two side blades of 160 mm each.
3. A middle blade of 250 mm and two side blades of 135 mm each.
4. A middle blade of 200 mm and one side blade of 160 mm
The results of this research can be found in Table 6-3, where every value represents the average of a number of
tests. The cutting forces in this table are scaled to the 200 mm blade to simulate a middle blade without side blades.
Table 6-3: The cutting forces on the side blades.
w=.15 m (1) w=.20 m (2) w=.25 m (3) w=.20 m (4)
hb/hi cr r cr r cr r cr r
30° 1 1.06 +26° 1.23 +14° 1.17 +11° 1.01 +13°
30° 2 0.78 +18° 0.87 +16° 0.83 +10° 1.14 +10°
30° 3 0.74 +22° 0.56 +22° 0.53 +11° 1.45 + 6°
45° 1 1.13 +23° 1.10 +14° 1.26 + 9° 1.04 + 5°
45° 2 0.94 +19° 0.94 +11° 0.93 + 7° 0.92 + 7°
45° 3 0.79 +14° 1.10 +17° 0.98 +11° 0.85 + 6°
60° 1 1.10 + 8° 1.10 + 6° 1.10 + 5° 1.04 + 2°
60° 2 0.94 +12° 1.10 + 8° 1.06 + 6° 0.91 + 2°
60° 3 0.77 + 8° 0.99 +15° 1.02 +11° 0.86 + 3°
The cutting force on the side blades in ratio to the cutting force on the middle blade cr, assuming that the cutting
process on the middle blade is two-dimensional. Also shown is the change of direction of the total cutting force
r. The cutting forces are scaled to the width of the middle blade for the blade widths 0.15 m (1), 0.20 m (2) and
0.25 m (3). The second column for w=.20 m (4) contains the results of the tests with only one side blade to measure
the side effects on the middle blade. The measured cutting forces are compared to the similar tests where two side
blades are used. The blade configurations are according to chapter 6.13.4. From this research the following
conclusions can be drawn:
1. For all blade angles the cutting force on the edge is larger than follows from the two-dimensional process, for
a blade-height / layer-thickness ratio of 1.
2. A blade-height / layer-thickness ratio of 2 or 3 shows a somewhat smaller cutting force with a tendency to
smaller forces with a higher blade-height / layer-thickness ratio.
3. The direction of the cutting force is, for all four blade configurations, aimed more downwards on the sides
than in the middle, where the differences with the middle blade decrease with a wider middle blade and
therefore less wide side blades. This implies that, with the widening of the middle blade, the influence of the
three-dimensional cutting process on the middle blade increases with a constant total blade width. This could
be expected. It also explains that the cutting force in the middle blade is directed more downwards with an
increasing middle blade width.
4. Blade configuration 4 differs slightly, as far as the magnitude of the forces is concerned, from the tendency
seen in the other three configurations with the 30 blade. The direction of the cutting forces match with the
other configurations. It has to be remarked that in this blade configuration the side effects occur only on one
side of the blade, which explains the small change of the cutting forces.
5. The measured transverse forces for blade configuration 4 are in the magnitude of 1% of the vector sum of the
horizontal and the vertical cutting forces and therefore it can be concluded that the transverse forces are
negligible for the used sand.
The conclusions found are in principle only valid for the sand used. The influence of the side effects on the
magnitude and the direction of the expected cutting forces will depend on the ratio between the internal friction of
the sand and the soil/steel friction. This is because the two-dimensional cutting process is dominated by both angles
of friction, while the forces that occur on the sides of the blade, as a result of the three-dimensional shear plane,
are dominated more by the internal friction of the sand.
Copyright © Dr.ir. S.A. Miedema TOC Page 171 of 454