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

Saturated Sand Cutting.
which the theoretical distribution is represented by the solid line. The water sub-pressures are made dimensionless,
although the weighted average permeability km is used instead of the permeability kmax used in the equations. From
this research the following conclusions can be drawn:
1. The measured forces and water sub-pressures show, in general, a good correlation with the theory.
2. The tendency towards increasing and more upward aimed forces with increasing blade angles can be observed
clearly in the Table 6-8 and Table 6-9.
3. The ratio between the measured and calculated forces becomes smaller when the blade angle and the bladeheight
/ layer-thickness ratio increase.
4. The cutting forces on the blade with the wear face are almost equal to the cutting forces on the blade with the
radius of rounding, but are slightly aimed more upward.
5. The ratio between the measured and calculated water sub-pressures is, in general, smaller than the ratio
between the measured and calculated cutting forces.
6. The measured water sub-pressures on the blade with the wear face and the blade with the radius of rounding
differ slightly (Table 6-10) from the water sub-pressures on the blade with the radius of rounding. On the 30
and the 45 blade, the water sub-pressures tends to smaller values for the blade with the wear face, although
the differences are very small. On the 60 blade these water sub-pressures are slightly higher. Therefore it can
be concluded that, for water pressures calculations, the wear-section-length / layer-thickness ratio w/h i has to
be chosen dependent of the blade angle. Which was already clear during the tests because the clearance angle
increased with a larger blade angle. For the determination of Appendix H to Appendix J, however, the ratio
used was w/h i=0.2, which is a good average value.
Table 6-8: Measured dimensionless forces.
measured
calculated
not-corrected corrected theoretical
hb/hi ct t ct t ct t
30° 1 0.54 +29.3° 0.49 +29.0° 0.39 +28.3°
30° 2 0.48 +27.5° 0.46 +27.2° 0.43 +27.4°
30° 3 0.49 +27.6° 0.46 +27.3° 0.43 +27.3°
45° 1 0.78 +15.1° 0.58 +13.9° 0.49 +12.9°
45° 2 0.64 +12.3° 0.59 +11.6° 0.57 +10.7°
45° 3 0.60 +11.0° 0.55 +10.5° 0.61 + 9.9°
60° 1 1.16 + 0.7° 0.77 - 0.6° 0.69 + 0.7°
60° 2 0.95 - 1.4° 0.79 - 2.2° 0.83 - 3.2°
60° 3 0.93 - 3.4° 0.82 - 4.0° 0.91 - 4.6°
60° 6 0.70 - 4.8° 0.64 - 5.7° 1.14 - 7.4°
Measured dimensionless forces, not-corrected and corrected for gravity and inertia forces and theoretical values
according to Appendix H to Appendix J for the blade with the radius of rounding and the sub-pressure behind the
blade. The theoretical values for ct and t are determined based on values for the angle of internal friction of 38,
a soil/steel angle of friction of 30 and a weighted average permeability of 0.000242 m/s, dependent on the weigh
factor a1.
Table 6-9: Measured dimensionless forces.
measured
calculated
not-corrected corrected theoretical
hb/hi ct t ct t ct t
30° 1 0.53 +26.2° 0.48 +25.9° 0.39 +28.3°
30° 2 0.48 +24.0° 0.46 +23.7° 0.43 +27.4°
30° 3 0.49 +24.7° 0.46 +24.3° 0.43 +27.3°
45° 1 0.72 +11.9° 0.57 +11.0° 0.49 +12.9°
45° 2 0.66 + 8.8° 0.60 + 8.3° 0.57 +10.7°
45° 3 0.63 + 7.8° 0.60 + 7.3° 0.61 + 9.9°
60° 1 ----- ----- ----- ----- ----- -----
60° 2 0.90 - 5.6° 0.80 - 6.2° 0.83 - 3.2°
60° 3 0.95 - 7.3° 0.87 - 8.0° 0.91 - 4.6°
60° 6 0.70 - 9.2° 0.64 -10.1° 1.14 - 7.4°
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