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1. Data compilation and evaluation
The development needs are based on an issue evaluation table which has been drafted in the first
months of the project and is regularly updated. An important issue derived from this table is the
model simulation of the evolution and especially the self-sealing of the Excavation Damaged Zone
(EDZ) which evolves as a result of the mechanical response of the rock to excavation of underground
openings. In the region close to the opening the dilatancy boundary will be exceeded, leading
to microfracturing and an associated increase of porosity and permeability of the salt rock. Existing
experimental data relevant for modelling this behaviour and the constitutive models used by
the different partners in their codes were compiled in a deliverable (D5 of the THERESA project,
THERESA 2007) in July 2007.
All constitutive models are able to simulate the elastic and the secondary creep behaviour of the
rock salt, regarding dilatancy and reconsolidation, however, different development states and levels
of confidence had been reached. Although many experimental data are available, reliable laboratory
data including volumetric defor-mation which are essential for dilatancy determination are scarce.
Therefore, GRS and BGR decided to perform additional laboratory tests outside the EC funding to
provide data for model calibration for those partners considering them useful.
2. Model improvement and calibration
While some of the partners (e. g., IfG, TUC) felt the existing data were sufficient for model calibration,
others used the additional lab tests to check their model parameters (FZK) or even modified
their model equations (CIMNE). In the meantime, model calibration has been widely completed. A
respective deliverable is currently under preparation. Figures 1 and 2 show some examples of results
from the GRS tests together with model calculations and Figures 3 and 4 verify the ability of
modelling softening and dilatancy as significant processes in the EDZ. All Figures illustrate the
high level obtained regarding model calibration.
Vertical stress (MPa)
30
-0.016
-0.014
25
-0.012
20
-0.010
-0.008
15
-0.006
-0.004
10
-0.002
5
Vertical stress
Vertical stress (test)
0.000
Volumetric strain
Volumetric strain (test) 0.002
0
0.004
0.00 0.02 0.04 0.06 0.08
Axial Strain (-)
Figure 1: Evolution of axial stress and volumetric strain of an Asse salt sample as a function of axial
strain, measured (GRS) and calculated (CIMNE)
490
Volumetric strain (-)