Stress-Strain Behavior of Jointed Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 87

The viscoplastic strain rates of a rock mass with n discontinuity sets D 1 to D n and a
schistosity S are calculated by superimposing the strain rates evaluated for the intact
rock and the different discontinuity sets:
(3.110)
Equation (3.110) presupposes that the strength of the intact rock, the strength of the
schistosity and the strength of the discontinuities are all exceeded. Otherwise, the ap-
propriate term needs to be omitted from the summation.
Stress determination
To determine the stresses, the total strains need to be subdivided into elastic and the
viscoplastic components:
(3.111)
Only the elastic strains lead to stresses for which the following applies according to (3.3):
(3.112)
The stresses are thus calculated from the total strains as follows:
(3.113)
Equation (3.113) represents the stress-strain relationship for an elastic-viscoplastic ma-
terial.
Summary and conclusions
In Table 3.1 the most important parameters are compiled that are required for
the description of the stress-strain behavior according to the proposed elastic-vis-
coplastic rock mechanical model (see also Figs. 2.36 and 2.37). In Table 3.1 the
methods for determination of these parameters, to be described in Chapters 13 to
18, are also specifi ed.
Not in every case do all the parameters need to be evaluated. In each particular case,
however, the parameters that are of considerable infl uence must be determined or at
least reliably estimated.