Engineering Rock Mechanics

Mechanical excavation 259

T

Drag pick

Button cutter

Disc cutter

Jet-assisted cutter

Figure 15.19 The action of four primary cutting devices.

The engineer wishes to know which cutting tool is the best, in what way
the tools should be configured on a machine cutting head, how to minimize
the need to replace the cutters, how to avoid damaging the cutter mounts,
and how to minimize vibration. This involves the use of experience,
empirical criteria as we have described, and varying the operating charac-
teristics (such as torque and thrust) during tunnel construction.

Villette limestone

depth of cut : 0.25 mm

350

300

250

200

150

100

50

0

L

50 100 150 200 250

Displacement (mm)

Figure 15.20 Record of tangential force during 250 mm cutting traverse using a drag

pick (after Almenara, 1992).