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

16.7. Chapter 7: Clay Cutting.
The Delft Sand, Clay & Rock Cutting Model.
16.7.1. Calc.: Cutting Forces.
Consider clay with cohesion of 200 kPa and an adhesion of 50 kPa. The strengthening factor is 2. A blade
angle of 55 degrees is used and a blade height of 0.1 m and blade width w=1 m. The layer thickness is 0.1 m.
Assume the Flow Type.
What is the ac ratio r?
ah 50
0.1 1
r (-)
ch 200
0.1 4
b
i
What is the shear angle?
See Figure 7-21 (Figure 7.20, 1 st edition), blade angle α=55 degrees and r=0.25 gives a shear angle β of about 57
degrees.
What are the horizontal and the vertical cutting forces?
Figure 7-23 (Figure 7.22, 1 st edition) gives a horizontal cutting force coefficient λHF of about 1.3 and Figure 7-24
(Figure 7.23, first edition) gives a vertical cutting force coefficient λVF of 0.6. This gives for the Flow Type:
F c h w 2 200 0.111.3 52 kN
h s i HF
F c h w 2 200 0.11 0.6 24 kN
v s i VF
16.7.2. Calc.: Cutting Forces & Mechanisms.
Consider clay with cohesion of 200 kPa and an adhesion of 10 kPa. The strengthening factor is 2. A blade
angle of 55 degrees is used and a blade height of 0.1 m and blade width w=1 m. The layer thickness is 0.1 m.
Assume the Flow Type.
What is the ac ratio r?
ah 10
0.1 1
r (-)
ch 200
0.1 20
b
i
What is the shear angle?
See Figure 7-21 (Figure 7.20, 1 st edition), blade angle α=55 degrees and r=0.05 gives a shear angle β of about 62
degrees.
What are the horizontal and the vertical cutting forces?
Figure 7-23 (Figure 7.22, 1 st edition) gives a horizontal cutting force coefficient λHF of about 1.1 and Figure 7-24
(Figure 7.23, first edition) gives a vertical cutting force coefficient λVF of 0.7. This gives for the Flow Type:
F c h w 2 200 0.111.1 44 kN
h s i HF
F c h w 2 200 0.11 0.7 28 kN
v s i VF
If the tensile strength is -20 kPa, will we have the Tear Type or the Flow Type?
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