The document summarizes the conclusions from three phases of the Joint Project on Constitutive Models for rock salt. Phase III identified needs for further development, including deformation at small stresses, tensile stresses, layer boundaries, and damage reduction. The new WEIMOS project will address these needs through additional laboratory tests, modeling improvements, and simulations to further validate and qualify constitutive models for analyzing long-term salt repository integrity.

1. Joint Project on Constitutive Models:
Conclusions from phases I – III and introduction of project WEIMOS
Washington, DC
September 7-9, 2016
Dr. Andreas Hampel
7th US/German Workshop on Salt Repository
Research, Design, and Operation

2. Dr. Andreas Hampel 2 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
In 2000, Udo Hunsche (BGR): Let’s perform a comparison of the models!
JP I (2004-2006): Development of a procedure
1. Perform systematic lab test series with certain salt types
 investigate (well-controlled in the lab) the various deformation phenomena
and their dependencies on in-situ relevant boundary conditions (~ seq, s3, T, de/dt)
2. Recalculate the lab tests
 determine a unique set of parameter values for each type of salt
 check the ability of the models to describe the various deformation phenomena
and the dependencies
=> constitutive model is prepared and valid to model various potential in-situ situations
3. Simulate real underground structures that display the considered phenomena
 check the suitability of the models
 compare the results with each other and with in-situ measurements
History (≈ 1980s – 1990s):
Constitutive models were developed by several groups (mostly independently)
based on numerous lab tests with rock salt and in-situ measurements in salt
-> How?

3. Dr. Andreas Hampel 3 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Joint Project series
Joint Project
(funded by)
Period
II
(BMBF)
2007 – 2010
Suitability to perform 3-D simulations of real underground
structures, incl. temporal extrapolations, calculation of
permeability in the DRZ of a highly-loaded pillar
III
(BMWi)
2010 – 2016
Modeling of the
• temperature dependence of deformation (-> HLW)
a) rock salt from Asse mine (domal salt),
b) rock salt from WIPP (bedded salt)
• damage reduction and healing (-> long-term integrity)
a) rock salt from Asse mine
I
(BMBF)
2004 – 2006
Modeling of the basic deformation phenomena in rock salt:
transient & steady-state creep, evolution of damage &
dilatancy, creep failure, post-failure behavior, residual strength
Main objectives:
document, investigate and compare constitutive models
and modeling procedures (par. determ., numerical calc.)

4. Dr. Andreas Hampel 4 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Joint Project I
Partner Constitutive Model Num. Program
BGR Hannover CDM JIFE
A. Hampel, Mainz CDM FLAC3D
IfG Leipzig Günther/Salzer Model, FLAC, FLAC3D
Minkley Model
KIT Karlsruhe KIT Model ADINA
Leibniz Universität Hannover (LUH), Lubby-MDCF Model FLAC3D
Technische Universität Clausthal (TUC), Lux/Wolters Model FLAC3D
Technische Universität Braunschweig (TUBS) TUBSsalt FLAC3D,
ANSYS
Sandia National Laboratories, Albuquerque MD Model (creep) Sierra Mechanics
and Carlsbad, NM, USA Code Suite
II

5. Dr. Andreas Hampel 5 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Recalculate a systematic series of lab tests with one salt type (example: clean salt from WIPP)
Creep tests at different temperatures and stress differences
Strength tests at different confining stresses
All tests were recalculated with a unique set of parameter values
, temperatures, and deformation rates

6. Dr. Andreas Hampel 6 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
the unique set of parameter valuesapplied stresses
TUC
test
1
TUC
test
2
Perform and recalculate systematic lab tests with one salt type (example: Speisesalz from Asse mine)
JP III: damage & dilatancy reduction and healing
dilatancy calculated with
individual parameter values
dilatancy calculated with

7. Dr. Andreas Hampel 7 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
JP I: Simulation of simple example structures
a) cylindrical specimen b) single drift c) room-pillar system

8. Dr. Andreas Hampel 8 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
JP II: a) Discretization study and b) 3-D simulation of an Angersdorf mine section
6x6 20x10
-6
-5
-4
-3
-2
-1
0
1
0 2 4 6 8 10 12 14 16 18 20
Pillar thickness [m]
Minimumprincipalstress[MPa]
In-situ frac test
AH simulation
IfG-GS simulation
IfG-Mi simulation
IUB simulation
TUC simulation
s3 [MPa]
d
example:
TUC

9. Dr. Andreas Hampel 9 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
JP III: Simulations of in-situ temperature influence and damage reduction & healing
a.1) IFC:
isothermal free
convergence
a.2) HFCP:
heated borehole
(Asse mine)
b) Bulkhead
(Asse mine)
6
7
8
9
10
11
12
13
14
0 0,01 0,02 0,03 0,04 0,05 0,06 0,07
heightalongboreholewall[m]
displacement [m]
ECN data
Hampel
Sandia
IfG-GS
LUH
KIT
TUC
TUBS
heated
zone
t_therm = 19 d (end of heating)
HFCP simulation

10. Dr. Andreas Hampel 10 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
JP III: Simulations of in-situ temperature influence
c.1) Room D (WIPP: bedded salt)
unheated -> at natural rock temperature
Simulated with unique parameter values from
recalculations of lab tests with WIPP salt

11. Dr. Andreas Hampel 11 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
JP III: Simulations of in-situ temperature influence and damage reduction & healing
c.2) Room B (WIPP, bedded salt)
heated after 354 days
Simulated with unique parameter values
from lab tests with WIPP salt
heated
heated

12. Dr. Andreas Hampel 12 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Conclusions from Joint Project phases I – III
We have developed a procedure to compare different constitutive models
 performance and recalculation of systematic lab tests
 simulations of typical in-situ situations
Constitutive models with a unique salt-type-specific set of parameter values
 are appropriate to describe various thermo-mechanical deformation phenomena
and their dependencies on in-situ relevant boundary conditions in a wide range
transient and steady-state creep,
evolution of damage and dilatancy,
creep failure and short-term strength,
post-failure behavior and residual strength,
(damage and dilatancy reduction and healing)
 are prepared to model various in-situ situations in rock salt
 some aspects need more experimental investigation and further development of
the modeling
-> new Joint Project WEIMOS
~ seq, s3, T, de/dt

13. Dr. Andreas Hampel 13 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
WEIMOS: Detailed investigation and further development of the modeling
convergence rates of Room B
I. Deformation at small, in-situ relevant deviatoric stresses
steady-state creep rates of WIPP salt
creep test with WIPP salt
at 4 and 2 MPa
WEIMOS:
 triaxial creep tests at RT and small Ds
 very stable boundary conditions
 strain measurement with very high resolution
-> WIPP salt

14. Dr. Andreas Hampel 14 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
WEIMOS: Detailed investigation and further development of the modeling
II. Stress and temperature dependence of damage reduction and healing
until now: only two TUC healing tests (Asse-Speisesalz)
with high resolution dilatancy measurements
Test 1 Test 2
?? healing rate ~ seq, s3, T, evol ??
=>
bulkhead simulation
WEIMOS:
 more healing tests at different T and Ds
 dilatancy measurements with very high resolution
-> WIPP salt

15. Dr. Andreas Hampel 15 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
WEIMOS: Detailed investigation and further development of the modeling
III. Deformation resulting from tensile stresses
Tensile
stresses
s3 > 0
Tensile
stresses
s3 > 0
IfG-G/S
strong temperature influence on dilatancy
(WIPP Rooms D and B)
-> influence of tensile stresses
Vergleich
Room D – Room B
300 K – erhitzt
t = 1354 Tage
(Room B)
0,0%
0,2%
0,4%
0,6%
0,8%
1,0%
1,2%
0 0,5 1 1,5 2
DilatanzdurchSchädigung
Spurlänge [m]
Spur T2 horizontal nach rechts
Room D
Room B
DRZ
WEIMOS:
started with basic calculation studies:
 bending beam
 Brazilian test

16. Dr. Andreas Hampel 16 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
WEIMOS: Detailed investigation and further development of the modeling
IV. Modeling of layer boundaries and interfaces
Munson et al. (1990):
Sandia Report SAND89-2671
WEIMOS:
• influence on convergence ?
(e.g. WIPP: sliding on clay seams)
• influence on damage and dilatancy in the DRZ ?
o lab: shear tests on layered salt specimens / blocks
(Sandia / RESPEC ?)
o in-situ experiments ?
 improved understanding of shear stresses & strains
 improved rock-mechanical modeling
 reduced uncertainties

17. Dr. Andreas Hampel 17 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Demonstration of improved modeling in WEIMOS
V. Virtual Demonstrator
Simulation of a complex model to demonstrate the improved modeling
of the various investigated phenomena
 small deviatoric stresses
 damage reduction and healing
 influence of interfaces/layer boundaries
 influence of e.g. thermally induced
tensile stresses
Simulation: step 1: open drift
step 2: installation of dam & backfill
step 3: post-operational phase and long-term behavior
rock salt
e.g. main drift

18. Dr. Andreas Hampel 18 / 18
7th US/German Workshop on Salt Repository Research, Design, and Operation
Washington DC, Sept. 07-09, 2016 Joint Project on Constitutive Models
Summary: Joint Project WEIMOS (April 2016 – March 2019)
Identified needs for further development:
1. Deformation behavior at small deviatoric stresses
2. Deformation behavior resulting from tensile stresses
3. Influence of inhomogeneities (layer boundaries, interfaces) on deformation
4. Influence of temperature and stress state on damage reduction
“Further Development and Qualification of the Rock Mechanical Modeling
for the Final HLW Disposal in Rock Salt”
Procedure:
 Laboratory tests, microstructural investigations, optional: in-situ measurements.
 Recalculations of the lab tests, simulations of basic examples and real in-situ structures.
 Further development of the rock mechanical modeling.
 Comparison of results, validation and qualification of the models and modeling procedures.
Main goal: Improved analysis and proof of long-term integrity
of the geological barrier rock salt (CRZ: Containment providing Rock Zone)