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Rock Mechanics.pdf - Mining and Blasting

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Figure 9.5 Stereographic projection<br />

of a plane, illustrating different domains<br />

for the upper <strong>and</strong> lower halfspaces<br />

of the plane (after Goodman,<br />

1989).<br />

Figure 9.6 Construction of great circles<br />

<strong>and</strong> identification of JPs for three<br />

joint planes.<br />

IDENTIFICATION OF POTENTIAL BLOCK FAILURE MODES – BLOCK THEORY<br />

60 ◦ /135 ◦ , the solid rock above the given plane is represented by the great circle<br />

marked EP in Figure 9.7(a). For the particular case of a plane horizontal roof of an<br />

excavation, the excavation pyramid is the solid rock in the half space above the roof.<br />

It is therefore the region inside the reference circle, as shown in Figure 9.7(b). For the<br />

south-east vertical wall of an excavation, the solid rock is on the south-east side of the<br />

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