Evaluation of Rock Mechanical Parameters - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 588

be close to the modulus E RM of the REV. However, the best way to determine E RM is to
use back analyses of monitoring results gained during full-scale excavations (Fig. 18.1,
lower).
Figure 18.1 Scale effect of rock mass deformation modulus
Also, the shear strength of discontinuities is scale dependent. In Section 3.3.1 discon-
tinuities were subdivided into different types with different strength criteria which are
compiled in Fig. 3.19.
The testing of relatively small discontinuity sections is sufficient to achieve shear pa-
rameters that are representative for planar and persistent discontinuities provided that
their surfaces are smooth or their surface roughness can be uniformly described at a
scale which compares to that of the investigated shear plane. Otherwise the measured
peak shear strength may be overestimated since the peak shear strength is scale depend-