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

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

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<strong>Rock</strong> <strong>Cutting</strong>: Atmospheric Conditions.<br />

A: Shear Angle β vs. Blade Angle α, Based on Shear Failure<br />

90<br />

Shear Angle β (Degrees)<br />

85<br />

80<br />

75<br />

70<br />

65<br />

60<br />

55<br />

50<br />

45<br />

40<br />

35<br />

30<br />

25<br />

20<br />

15<br />

10<br />

5<br />

0<br />

15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100<br />

Blade Angle α (Degrees)<br />

φ=00°<br />

φ=05°<br />

φ=10°<br />

φ=15°<br />

φ=20°<br />

φ=25°<br />

φ=30°<br />

φ=35°<br />

φ=40°<br />

φ=45°<br />

© S.A.M.<br />

Figure 8-41: <strong>The</strong> shear angle with limitation.<br />

Figure 8-41 shows the shear angle with limitations. <strong>The</strong> limitations occur because at a certain sum of the blade<br />

angle, the shear angle and the angle of internal friction, a positive tensile strength would be required to get brittle<br />

tensile failure, which is physically impossible. Compressive stresses are defined positive and tensile stresses<br />

negative, so a positive tensile stress would in fact be a compressive stress. Beyond this limitation only brittle shear<br />

can exist, or if the sum of the angles is to high, probably another mechanism like the wedge mechanism.<br />

Copyright © Dr.ir. S.A. Miedema TOC Page 285 of 454

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