Structure of Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 24

to rock engineering applications. A detailed description of this method is given in Müller
(1963), Adler et al. (1969), Hoek & Bray (1977), Goodman (1980), Hoek & Brown (1980b),
Priest (1985), Wittke (1990) and in various geological and rock mechanical textbooks.
The lower hemisphere of a unit sphere is denoted as the “lower reference hemisphere”.
The representation of the discontinuity's orientation into the lower reference hemi-
sphere is shown in Fig. 2.26. A discontinuity forming a tangent plane on the lower ref-
erence hemisphere can be characterized by its contact point referred to as a “pole”. This
is illustrated in Fig. 2.26 (upper) by means of a vertical discontinuity (A), a horizontal
discontinuity (B) and an oblique discontinuity (C). Thus, the orientation of a discon-
tinuity is well-defined by the location of its pole. The intersection of a discontinuity
running through the center of the reference hemisphere and the surface of the lower
reference hemisphere is a great circle, and the normal of the discontinuity intersects the
surface of the lower reference hemisphere at its pole (Fig. 2.26, lower).
Figure 2.26 Orientation of discontinuities (A, B, C), representation in the lower reference hemisphere