Swelling Rock - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 199

some colleagues that the swelling of Gypsum Keuper cannot be correctly described
by this swelling law (Kirschke 1995, Anagnostou 2007, Pimentel 2007, Anagnostou
et al. 2010, Kirschke 2010). Figure 8.17 shows the vertical swelling strains evaluated
from the test results as a function of vertical stress at full saturation of specimens
(

= 1). A regression analysis led to mean swelling parameters of K q = 0.16 and
σ q0 (

ω

ω = 1) = 10.2 MPa (Wahlen 2009).

Figure 8.16 Results of a swelling test on a specimen of unleached Gypsum Keuper, measured strains as
well as measured and extrapolated stresses (Wahlen 2009)

The interpretation of long-term laboratory swelling pressure tests ( = 0) on intact rock

specimens such as the one represented in Fig. 8.9 indicate water uptake coefficients D W
ranging from 3 · 10 -13 m2/s to 4 · 10 -12 m 2 /s.
The volumetric anhydrite fraction of the unleached Gypsum Keuper was found to vary
mostly between 0.05 and 0.6, corresponding to S W values of 0.04 to 0.47 if the swelling
of corrensite is not considered (Wahlen 2009).

ε

In Table 8.1, the characteristic values of the essential parameters which were evalu-
ated for certain layers of the unleached Gypsum Keuper in the area of Stuttgart are
compiled. In addition, the methods of determination of these parameters are speci-
fied. Most of the parameters can be reliably estimated from the results of mapping,
laboratory tests and field tests. Only S W as well as the shear parameters and the
dilatancy angles of the discontinuities needed to be evaluated from back analyses
(Section 8.8).