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

Rock Cutting: Atmospheric Conditions.
Shear Angle β (Degrees)
© S.A.M.
A: Shear Angle β vs. Blade Angle α, Based on Shear Failure
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Blade Angle α (Degrees)
φ=00°
φ=05°
φ=10°
φ=15°
φ=20°
φ=25°
φ=30°
φ=35°
φ=40°
φ=45°
Figure 8-30: The shear angle β as a function of the blade angle α and the angle of internal friction φ.
Based on equation (8-97) and (8-109) the specific energy Esp can be determined according to:
E
sp
Pc Fh
vc Fh
HF
c
Q h w v h w
i c i
(8-114)
The cohesive shear strength c is a function of the Unconfined Compressive Strength UCS and the angle of internal
friction φ according to (see Figure 8-36):
UCS 1
sin
c 2
cos
(8-115)
This gives for the specific energy Esp:
E
sp HF HF
UCS 1
sin
c 2
cos
(8-116)
Figure 8-33 shows the specific energy Esp to UCS ratio. In Figure 8-30, Figure 8-31, Figure 8-32 and Figure 8-33
an example is given for an α=60º blade and an internal friction angle of φ=20º.
It should be noted again that the forces and the specific energy are based on peak values. For the average this
should be multiplied with a factor between 0.5 and 1.0, but closer to 0.5.
Copyright © Dr.ir. S.A. Miedema TOC Page 277 of 454