Page 266 - Rock Mechanics For Underground Mining

EXCAVATION DESIGN IN BLOCKY ROCK

(a) Reference circle

EP

(b) Reference circle

EP

(c) Reference
circle

EP

Figure 9.7 (a) The EP for a plane
surface of an excavation where the
solid rock lies above the plane; (b) the
EP for the roof of a mine excavation;
(c) the EP for the SE vertical wall of
an excavation.

Figure 9.8 (a) Construction of the
great circles and JPs for the joint
sets oriented 30 /90 ,60 /45 and
◦
◦
◦
◦
20 /330 ; (b) JP 101, the only JP that
◦
◦
has no intersection with the EP for the
roof (after Goodman, 1989).
vertical plane represented by the NE-SW trending line along the extended diameter
of the reference circle, shown in Figure 9.7(c), so the EP is represented by the shaded
part of the projection.
9.2.3 Application in stability analysis
Excavation roof. Having established methods for constructing the JPs and EP for
a blocky rock mass and the boundaries of an excavation, the topological test for
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