Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 413

cycles as illustrated in Fig. 14.4. The deformability for initial loading, unloading and
reloading can then be determined separately for each cycle. The stress-strain curves for
unloading and reloading often can be considered as equal (Fig. 14.4).
At the points of load reversal the specimen may be held under constant load in or-
der to indicate an eventual time-dependent behavior of the intact rock prior to failure.
Fig. 14.5 shows corresponding stress-strain curves (DGGT 2004b).

Figure 14.5 Loading and unloading cycles including constant load phases (DGGT 2004b)

According to Wittke (1990), the elastic constants E 1 , E 2 , G 2 , ν 2 of transversely

isotropic intact rock, defi ned in Section 3.2.1, can be determined from test series on
specimens that are prepared with different inclinations

ν 1 and

of the isotropic plane with
respect to the end faces of the specimen (Fig. 14.2). The elastic constants E 2 and

β

ν 2 can

be determined from tests carried out on specimens with β = 0 as

(14.17)

(14.18)