Engineering Rock Mechanics

Specialized blasting techniques 253

c

Figure 15.14 Illustration of pre-splitting effect in model tests in Perspex with

introduced discontinuities (from Worsey, 1981).

The pre-split mechanism we have discussed, and the associated factors
affecting the outcome, have been investigated and reported by Worsey
(1981). In Figs 15.14 and 15.15 there are sets of three photographs illustrating
the creation of pre-split planes in model tests utilizing Perspex (polymethyl-
methacrylate) and rock. These photographs illustrate many of the points
discussed, and the reader should note the clear evidence, in the tests
conducted using Perspex, of the reflected stress wave, and the robustness of
the pre-splitting technique almost regardless of the discontinuity orientation.

Figure 15.15 Illustration of pre-splitting effect in model tests in rock with
introduced discontinuities (from Worsey, 1981).