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

Rock Cutting: Hyperbaric Conditions.
The vertical cutting force coefficient λVF is positive downwards directed. From the calculations it appeared that
for a 60 degree blade, the Curling Type will already occur with an hb/hi=1. For a 110 degree blade it requires an
hb/hi=4-5, depending on the internal friction angle. The transition at small hb/hi ratios, between the Flow Type
and the Curling Type, will occur at blade angles between 60 and 90 degrees. So its important to determine the
cutting forces for both mechanisms in order to see which of the two should be applied. This is always the
mechanism resulting in the smallest horizontal cutting force.
100
Horizontal Cutting Force Coefficient λ HF vs.
Hydrostatic Pressure/Shear Strength Ratio r z
φ=01°
Horizontal Cutting Force Coefficient λ HF (-)
10
φ=05°
φ=10°
φ=15°
φ=20°
φ=25°
φ=30°
φ=35°
© S.A.M.
.M.
1
0.1 1.0 10.0 100.0
Hydrostatic Pressure/Shear Strength Ratio r z (-)
Figure 9-9: The horizontal cutting force coefficient λHF for a 60 degree blade, hb/hi=1.
φ=40°
2
Vertical Cutting Force Coefficient λ VF vs.
Hydrostatic Pressure/Shear Strength Ratio r z
φ=01°
Vertical Cutting Force Coefficient λ VF (-)
0
-2
-4
-6
-8
φ=05°
φ=10°
φ=15°
φ=20°
φ=25°
φ=30°
φ=35°
© S.A.M.
.M.
-10
0.1 1.0 10.0 100.0
Hydrostatic Pressure/Shear Strength Ratio r z (-)
Figure 9-10: The vertical cutting force coefficient λVF for a 60 degree blade, hb/hi=1.
φ=40°
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