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

The Delft Sand, Clay & Rock Cutting Model.
Figure 1-1: Different types of dredging equipment.
At large blade angles, the theory of the 2D cutting process at small blade angles can no longer be valid. This theory
would give very large and even negative cutting forces which is physically impossible. The reason for this is a sine
in the denominator of the generic cutting force equation containing the sum of the blade angle, the shear angle, the
internal friction angle and the external friction angle. If the sum of these 4 angles approaches 180 degrees, the sine
will become very small resulting in very high cutting forces. If the sum of these 4 angles exceeds 180 degrees, the
sine is negative resulting in negative cutting forces. Nature will find another mechanism which is identified as the
wedge mechanism. In front of the blade a wedge will occur, with an almost fixed wedge angle, reducing the cutting
forces. Chapter 10: The Occurrence of a Wedge describes the generic theory for the occurrence of a wedge in front
of the blade.
The following chapters give the theory of soil cutting at large blade angles that will enable the reader to determine
the cutting forces, powers and production in different types of soil.
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