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

A Wedge in Hyperbaric Rock Cutting.
Chapter 15:
A Wedge in Hyperbaric Rock Cutting.
15.1. Introduction.
For completeness of the overview the equations for the cutting of the wedge mechanism for hyperbaric rock are
given here without further explanation.
Figure 15-1: Definitions.
Definitions:
1. A: The wedge tip.
2. B: End of the shear plane.
3. C: The blade top.
4. D: The blade tip.
5. A-B: The shear plane.
6. A-C: The wedge surface.
7. A-D: The wedge bottom.
8. D-C: The blade surface.
9. hb: The height of the blade.
10. hi: The thickness of the layer cut.
11. vc: The cutting velocity.
12. α: The blade angle.
13. β: The shear angle.
14. Fh: The horizontal force, the arrow gives the positive direction.
15. Fv: The vertical force, the arrow gives the positive direction.
15.2. The Equilibrium of Forces.
Figure 15-2 illustrates the forces on the layer of soil cut. The forces shown are valid in general for each type of
soil.
The forces acting on the layer A-B are:
1. A normal force acting on the shear surface N1, resulting from the effective grain stresses.
2. A shear force S1 as a result of internal friction N1·tan(φ.
3. A force W1 as a result of water under pressure in the shear zone.
4. A shear force C1 as a result of pure cohesion c or shear strength. This force can be calculated by multiplying
the cohesive shear strength c with the area of the shear plane.
5. A force normal to the pseudo blade N2, resulting from the effective grain stresses.
6. A shear force S2 as a result of the soil/soil friction N2·tan(λ between the layer cut and the wedge pseudo
blade. The friction angle λ does not have to be equal to the internal friction angle φ in the shear plane, since
the soil has already been deformed.
Copyright © Dr.ir. S.A. Miedema TOC Page 393 of 454