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

Saturated Sand Cutting.
10
Partial Cavitation
9
Pore Pressure (m.w.c.)
8
7
6
5
4
3
2
1
0
vc=0.4 m/s vc=0.5 m/s vc=0.6 m/s vc=0.8 m/s
vc=0.9 m/s vc=1.1 m/s vc=1.2 m/s vc=1.3 m/s
Figure 6-50: Partial cavitation limited by dissolved air, α=45º, hi=7cm.
6.13.11. Determination of and from Measurements.
The soil/steel friction angle δ and the angle of internal friction φ can be determined from cutting tests. Sand without
cohesion or adhesion is assumed in the next derivations, while the mass of the cut layer has no influence on the
determination of the soil/steel friction angle. In Figure 6-51 it is indicated which forces, acting on the blade, have
to be measured to determine the soil/steel friction angle δ.
The forces Fh and Fv can be measured directly. Force W2 results from the integration of the measured water
pressures on the blade. From this figure the normal force on the blade, resulting from the grain stresses on the
blade, becomes:
Fn W2 W3 Fh sin( ) Fv cos( )
(6-110)
The friction force, resulting from the grain stresses on the blade, becomes:
Fw Fh cos( ) Fv sin( )
(6-111)
The soil/steel angle of friction now becomes:
Fw
arctan
F n
(6-112)
Determination of the angle of internal friction from the cutting tests is slightly more complicated. In Figure 6-52
it is indicated which forces, acting on the cut layer, have to be measured to determine this angle. Directly known
are the measured forces Fh and Fv. The force W1 is unknown and impossible to measure. However from the
numerical water pressures calculations the ratio between W1 and W2 is known. By multiplying the measured force
W2 with this ratio an estimation of the value of the force W1 can be obtained, so:
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