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

6.12. Specific Cutting Energy.
The Delft Sand, Clay & Rock Cutting Model.
In the dredging industry, the specific cutting energy is described as:
The amount of energy, that has to be added to a volume unit of soil (e.g. sand) to excavate the soil.
The dimension of the specific cutting energy is: kN/m² or kPa for sand and clay, while for rock often MN/m 2 or
MPa is used.
Adhesion, cohesion, gravity and the inertia forces will be neglected in the determination of the specific cutting
energy. For the case as described above, cutting with a straight blade with the direction of the cutting velocity
perpendicular to the blade (edge of the blade) and the specific cutting energy can be written:
E
sp
Fh
vc Fh
h w v h w
i c i
(6-88)
The method, with which the shear angle is determined, is therefore equivalent with minimizing the specific
cutting energy, for certain blade geometry and certain soil mechanical parameters. For the specific energy, for the
non-cavitating cutting process, it can now be derived from equations (6-71) and (6-88), that:
E c g v h (6-89)
k
nc 1 w c i
m
For the specific energy, for the fully cavitating cutting process, can be written from equations (6-74) and (6-88):
ca 1 w
E d g z 10
(6-90)
From these equations can be derived that the specific cutting energy, for the non-cavitating cutting process is
proportional to the cutting velocity, the layer-thickness and the volume strain and inversely proportional to the
permeability. For the fully cavitating process the specific cutting energy is only dependent on the water depth.
Therefore it can be posed, that the specific cutting energy, for the fully cavitating cutting process is an upper limit,
provided that the inertia forces, etc., can be neglected. At very high cutting velocities, however, the specific cutting
energy, also for the cavitating process will increase as a result of the inertia forces and the water resistance.
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