Structure of Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 17

2.7 Rock Mass

2.7.1 Examples
Figure 2.14 shows a granite in which the jointing in preferred directions is clearly visible.
The sandstone represented in Fig. 2.15 exhibits horizontal, persistent and closed bed-
ding-parallel discontinuities, as well as vertical joints that frequently terminate at the
bedding-parallel discontinuities. Locally, open joints appear.
Fig. 2.16 shows a closely bedded claystone with vertical joints. After drying and sub-
sequent contact with water, such a rock may become a mud. A rock mass with such a
behavior is called “slaking”.

A sedimentary rock mass often consists of an alternating sequence of different intact
rocks. In the example illustrated in Fig. 2.17, between sandstone and siltstone layers
bedding-parallel shear zones appear.

Figure 2.15 Bunter (sandstone), near Fulda (Germany)