Site Investigation - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 373

ever, since the direction of the cavern axis is frequently not selected until the exploration
results are available it is advisable to arrange the exploration adits above the planned cav-
ern (Fig. 13.16). Thus, cross-cuts can also be excavated without the risk that they may cut
through the later wall of the cavern and weaken the rock mass in this area (Wittke 1990).
Figure 13.16 Arrangement of exploration adits for caverns (Wittke 1990)
Exploration adits for the foundation of a dam should be located along the abutments or
in the downstream area (Fig. 13.17). Adits directed longitudinal to the valley from the
upstream to the downstream side should be avoided altogether. Even if such an adit is
to be backfilled afterwards, the risk of a connection being established between upstream
and downstream cannot always be completely ruled out (Wittke 1990).
Figure 13.17 Arrangement of exploration adits for the foundation of a dam (Wittke 1990)