Laboratory Tests - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 411

Figure 14.3 Example for the arrangement of axial and lateral displacement transducers (DGGT 2004b)

The radial strain D of the specimen

during the test measured by lateral displacement transducers arranged in the middle
part of the specimen (Fig. 14.3, lower):

ε r can be calculated from the diameter change Δ

(14.13)

where D is the initial diameter of the specimen (Fig. 14.2).
The tangential strain ε t of specimens with isotropic deformability may be determined

by measuring perimeter changes in the middle part of the specimen using circumferen-
tial displacement transducers (ISRM 1999a, DGGT 2004b).

For isotropic stress-strain behavior the elastic constants E IR and ν IR of intact rock can

be determined from the increments of stress and strain measured during the test as
illustrated in Fig. 14.4:

(14.14)

(14.15)