Stress Measurements - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 538

Figure 16.19 Exploration and field testing for the underground powerhouse cavern of the
pumped-storage plant Estangento-Sallente (Soria & Wittke 1985)

The northern part of the powerhouse cavern is located in granite formed by intrusions
of molten rock consisting of granodiorites, which contain numerous quartz and aplite
veins. The remaining part of the cavern lies in metamorphic rock which has been cre-
ated by a contact metamorphism in the transition from the granite to the surrounding
schistose rock (Fig. 16.19). The metamorphic rock consists of corneans, quartz-phyl-
lites, phyllites, quartz-schists and schists, but does not exhibit a schistosity, since the
primary structure of the original rock disappeared during metamorphosis.

Among others, the exploration, testing and monitoring program for the cavern included
core drillings and mappings in the two exploration adits, laboratory tests, dilatometer
tests, LFJ tests and triaxial cell measurements (Fig. 16.19).
The results of the triaxial cell measurements are represented in Fig. 16.20. Accordingly,
the maximum principal normal stress σ 1 is oriented horizontally and normal to the cav-

ern axis. The intermediate principal normal stress σ 2 is also oriented horizontally but

parallel to the cavern axis, while the minimum principal normal stress

σ 3 is oriented ver-
tically. The high horizontal stresses were considered to be tectonic stresses (Section 9.3).