Rock Salt - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 124

The model of Hou and Lux (Hou 1997, Hou 2003, Hou & Lux 2002) describes the
three phases of creep, failure, post-failure behavior, healing and also a reduction of
the elastic constants with the degree of damage, and is based on the model of Lux
(1984). For tertiary creep and creep failure, approaches from the constitutive models of
Cristescu & Hunsche (1996), Chan et al. (1994), Chan et al. (1995) and Aubertin et al.
(1998) were adopted.
A comparative consideration of these constitutive models can be found in Hou et al.
(2007) and Schulze et al. (2007).

5.3 Validation of Model

Figure 5.4 illustrates the results of two uniaxial creep tests each carried out with the
two stress levels σ 1 = 14 MPa on specimens of two different types

of rock salt (“Hangendsalz” and “Hauptsalz”) from the salt dome “Gorleben” in Ger-
many (Hunsche 1994). In these tests only primary and secondary creep occurred. The
different creep behavior of the two types of rock salt could be back analyzed by sets of
parameters that primarily differ with respect to the parameter

σ 1 = 12 MPa and

η s describing steady-state

creep (Wittke 2000b).

Figure 5.4 Back analysis of two uniaxial creep tests on rock salt from the salt dome Gorleben
(Germany using the stress-strain law of WBI (Wittke 2000b)