Civil Engineering Reference
In-Depth Information
Information gathered during exploration indicated that the rock in the area of the
pumped storage plant is part of the massif at the south end of the “La Maladeta” gran-
ite batholyth being formed by intrusions of molten rock consisting of granodiorites.
These intrusions have created a contact metamorphism in the area of the transition
from the granite to the surrounding schistose rock leading to a metamorphic rock, the
so-called “Cambro Ordovician material” (Fig. 22.6). Both rock types existing in the
project area, the granite and the metamorphic rock, were described in Section 16.7.1.
The largest part of the powerhouse cavern lies in metamorphic rock. Only a short sec-
tion of the northern part of the cavern is located in granite (Fig. 16.19).
Figure 22.6
Geologic map of project area (Wittke 1990)
22.2.2 Discontinuities
In the exploration adits a detailed mapping was carried out with regard to orientation,
extent, spacing and filling of discontinuities.
The pole plot represented in Fig. 22.7 (left) shows the orientations of a total of 1068
discontinuities measured in the adit sections located in metamorphic rock. As a result,
the discontinuities can be grouped into three discontinuity sets, Sch, D1 and D2. The
abbreviation Sch is used for the discontinuities that are oriented parallel to the schistos-
ity in the schists and phyllites existing in the project area. The discontinuities of sets Sch
and D1 appear most frequently, and on average form angles of 50° and 45°, respectively,
with the cavern axis. The mean dip of the less frequently appearing discontinuities of
set D2 is vertical. Since Sch and D1 predominantly dip under 45° to north and south,
respectively, these two sets intersect each other on average at an angle of 90°.
The pole plot represented in Fig. 22.7 (right) shows the orientations of master joints
with large extent containing both sandy-clayey and quartz fillings. Most of them follow
the orientations of sets Sch and D1.
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