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

The Delft Sand, Clay & Rock Cutting Model.
1. A hydrostatic pressure along the boundary.
2. A boundary as an impermeable wall.
3. A combination of a known pressure and a known specific flow rate.
Figure 12-9: The boundaries of the FEM model.
None of these choices complies with the real process. Water from outside the calculation area will flow through
the boundary. This also implies, however, that the pressure along this boundary is not hydrostatic. If, however, the
boundary is chosen with enough distance from the real cutting process the boundary condition may not have an
influence on the solution. The impermeable wall is chosen although this choice is arbitrary. Figure 12-14 and
Figure 12-16 give an impression of the equipotential lines and the stream lines in the model area. Figure 12-10
show the dimensionless pore pressure distributions on the lines A-B, A-C, A-D and D-C. The average
dimensionless pore pressures on these lines are named p1m, p2m, p3m and p4m.
Figure 12-10: Pore pressure distribution on the shear plane A-B, the bottom of the wedge A-D, the blade
D-C and the front of the wedge A-C.
If there is no cavitation the water pressures forces W1, W2, W3 and W4 can be written as:
2
1m w c i
p g v h w
W1
k sin( )
And
max
p2m w g vc hi hb
w
W2
k sin( )
max
(12-23)
(12-24)
And
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