10 Current status of research in the Joint Project WEIMOS

Current Status of Research in the Joint Project WEIMOS

Andreas Hampel (Consultant), Till Popp (IfG), Kai Herchen (TUC)

8th US/German Workshop on Salt Repository Research,

Design, and Operation

Middelburg, The NetherlandsSeptember 5-7, 2017

WEIMOS:Verbundprojekt: Weiterentwicklung und Qualifikation der gebirgsmechanischen Modellierung für die HAW-Endlagerung im Steinsalz

Joint Project: Further Development and Qualification of the Rock Mechanical Modeling for the Final HLW Disposal in Rock Salt

Institut für Gebirgsmechanik

GmbH LeipzigDr. Andreas HampelWissenschaftlicher Berater / Scientific Consultant

8th US/German Workshop on Salt Repository Research, Design, and Operation

Dr. Andreas HampelWissenschaftlicher Berater / Scientific Consultant


GmbH 2WEIMOS

Joint Project WEIMOS

Partners

Germany:

Dr. Andreas Hampel, Mainz (Coordinator)

Institut für Gebirgsmechanik GmbH (IfG), Leipzig

Leibniz Universität Hannover (LUH)

Technische Universität Braunschweig (TUBS)

Technische Universität Clausthal (TUC)

United States:

Sandia National Laboratories, Albuquerque & Carlsbad

(associated partner, i.e. not funded by BMWi)




GmbH 3WEIMOS

Joint Project Period Objective Subjects: Modeling of ...

I 2004-2006

Studies and comparisons

of constitutive models and

calculation procedures

for the thermomechanical

behavior of rock salt

basic deformation

phenomena (creep, damage,

dilatancy, failure, ...)

II 2007-20103-D deformation, temporal

extrapolation, permeability

III 2010-2016temperature influence,

damage reduction & healing

WEIMOS 2016 – 2019Further development and qualification of the rock

mechanical modeling for the final HLW disposal in rock salt

Joint Project Series

Aim: Improved analysis and proof of the long-term integrity of the geological barrier rock salt

around an underground repository for all types of radioactive waste (incl. HLW)




GmbH 4WEIMOS

WP 1: Deformation behavior at small deviatoric stresses

WP 2: Influence of temperature and stress state on

damage reduction

WP 3: Deformation behavior resulting from tensile stresses

WP 4: Influence of inhomogeneities (layer boundaries,

interfaces) on deformation

WP 5: Virtual demonstrator

WP 6: Administrative work




damage reduction


Till Popp (IfG)

Kai Herchen (TUC)

Till Popp (IfG)

Andreas Hampel

presented by

Andreas Hampel

Work Packages




GmbH 5WEIMOS

WEIMOS WP 4: Influence of inhomogeneities (layer boundaries, interfaces)

Munson et al. (1990):

Sandia Report SAND89-2671

Important questions:

• Influence on convergence?

(e.g. sliding on clay seams at WIPP)

• Influence on damage and dilatancy in the DRZ?

• Modeling of these phenomena?

Experimental investigations

RESPEC lab: shear tests on layered rock salt specimens

Proposals of Sandia (1983, 2016): In-situ experiments

Objective:

Study, develop further and improve the modeling

=> Reduce uncertainties of simulation results,

increase confidence in the results

Stratigraphy at WIPP

current status:

upcoming drilling of layered salt cores at Intrepid mine near WIPP:

rock salt with clay seams, salt/anhydrite, salt/polyhalite interfaces




GmbH 6WEIMOS

WEIMOS WP 5: Virtual demonstrator

Objective: 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

Simulations: step 1: open drift

step 2: installation of the dam

step 3: post-operational phase & long-term behavior

rock salt




GmbH 7WEIMOS

rock salt

WEIMOS WP 5: Virtual demonstrator

current status:

extrude the plane strain model of Room D from Joint Project III to 3-D,

add one or two clay seams,

perform test simulations (find appropriate discretization, ...)

Joint Project III:

2-D vertical cut

at Room D

Virtual Demonstrator

clean salt

argil. salt

anhydrite

polyhalite

WEIMOS:

preliminary VD model




GmbH 8WEIMOS


Work Packages



damage reduction






Till Popp (IfG)

Kai Herchen (TUC)

Andreas Hampel

presented by

Andreas Hampel

Till Popp (IfG)




GmbH 9WEIMOS

WP 1: Deformation behavior at small deviatoric stresses Motivation

The challenge …,how does salt deform in the long term?

Boundary conditions:Fore cast period: 103 < time (years) < 106

Deformations: 0.1 < e < 1Temperatures: 20°C - 200°CDef. Rates: 1∙10-17 < e (1/s) < 3∙10-11

Creep mechanisms:Pressure solution creep vs. dislocation creep

Test duration is usually limited!

modified after Urai, 2012

Deformation-mechanism map

0.1

Dislocation creep

Pressure

Solution

Creep

In situ

labn = 1

n = 5




GmbH 10WEIMOS

WP 1: Deformation behavior at small deviatoric stresses Comparison of different investigations

BGR (2016): Type ERAM salt, Ø=100 mm L = 200 m, t < 1.4a

Berest et al. (2015): Salt mine Varangeville

- Type Avery Island salt, t < 1.5 a

Berest et al. (2017): Salt mine Altaussee - Type: Avery Island, Hauterives, Gorleben t ≈ 2 a

Dead weight

setup

Sample size: Ø=70

mm L = 140 m

3D-simulation of salt dome uplift

"humid"

bedded

salt

"wet" salt

glacier

Residual stress?

"dry" salt

dome




GmbH 11WEIMOS

WP 1: Deformation behavior at small deviatoric stresses IfG – improved creep rigg

Axial Force: 200 kN

Sample size:

= 60mm,

l = 120mm

Capacitive displacement

system

Quartz rod

CSH02FL-CRm1,4

Resolution 0.15 nm

Linearity 0,05 m

Temperature sensitivity -2.4 nm/°C

Measuring principle

The principle of capacitive displacement

measurement using the capaNCDT

(capacitive Non-Contact Displacement

Transducer) system is based on how an

ideal plate-type capacitor operates. The

two plate electrodes are represented by

the sensor and the opposing

measurement object




GmbH 12WEIMOS

1.0E-09

1.0E-08

1.0E-07

1.0E-06

1.0E-05

1.0E-04

1.0E-03

1.0E-02

1.0E-01

1.0E+00

0.1 1 10

Cre

ep

Rate

[1

/d]

Difference Stress [MPa]

wipp clean salt T=27°C



T=30°C - GS

T=30°C - Mi

T=60°C - GS

T=60°C - Mi

T=80°C - GS

T=80°C - Mi

2016/17 T=25°C

2016/17 T=60°C

2016/17 T=80°C

2016/17 T=100°C

WP 1: Deformation behavior at small deviatoric stresses Lab program / current data base

IfG lab program

No. TDuration

[d]

s1

[MPa]

s3 = p

[MPa]

Ds

[MPa]

TCC

24

25°C

60°C

10

50

80

80

80

20

28

26

26

26

20

22

0

8

6

4

4

TCC

21

25°C

60°C

10

50

80

80

80

20

26

24

24

24

20

22

0

6

4

2

2

TCC

22

25°C

60°C

10

50

80

80

80

20

24

22

22

22

20

21

0

4

2

1

1

TCC

23

80°C 10

50

80

80

80

20

28

26

26

26

20

22

20

0

8

6

4

6

TCC

27

80°C 10

50

80

80

80

20

26

24

24

24

20

22

20

0

6

4

2

4

TCC

29

80°C 10

50

80

80

80

20

24

22

22

22

20

21

0

4

2

1

1

TCC

28

25°C

25°C

40°C

60°C

80°C

100°C

10

50

50

50

50

50

20

24

24

24

24

24

20 0

4

4

4

4

4




GmbH 13WEIMOS

WP 1: Deformation behavior at small deviatoric stresses Modelling of Salt Dome Recent Uplift Rate

Example: Development of salt dom Gorleben-Rambow

Recent Uplift Rate

Target Value:

0.01….0.05 mm/a




GmbH 14WEIMOS

WP 1: Deformation behavior at small deviatoric stresses The generic model – current situation

12 km

Triassic/ Jurassic r= 2,45 g/cm³

Cretaceous

r = 1,8 g/cm³

r = 2,32 g/cm³

Upper Permian

(Rock Salt )

r = 2,17 g/cm³

Tertiary, Quaternary

3,5

km

r = 2,33 g/cm³

Lower Permian




GmbH 15WEIMOS

WP 1: Deformation behavior at small deviatoric stresses Outcome with the BGRa - approach

Vertical Velocity - after 1 Mio yearsZ-vel

in m/day

5E-10 m/d = 1.8E-4 mm/yrs

v. Mises Stress

seff<1MPA

8E-5 mm/yrs

Recent Uplift Rate

Target Value:

0.01….0.05 mm/a




GmbH 16WEIMOS

WP 1: Deformation behavior at small deviatoric stresses Outcome with the IfG-GS Model

Vertical Velocity - after 1 Mio yearsZ-vel

in m/day

9E-8 m/d = 0.032 mm/yrs0.03 mm/yrs

v. Mises Stress

seff<1MPA

approx. 3 orders of magnitude

Recent Uplift Rate

Target Value:

0.01….0.05 mm/a




GmbH 17WEIMOS

WP 3: Deformation behavior resulting from tensile stresses The problem

• Tensile strength and tensile damage processes play dominant roles for development of micro-cracks and progressive damage, usually described by the term “Excavated Damage Zone” (EDZ).

• Tensile stresses may be generated by thermal effects during heating or cooling.

Asse

WIPP




GmbH 18WEIMOS

WP 3: Deformation behavior resulting from tensile stresses The approach

• Tensile strength and tensile damage processes play dominant roles for development of micro-cracks and progressive damage, usually described by the term “Excavated Damage Zone” (EDZ).

• Tensile stresses may be generated by thermal effects during heating or cooling.

WEIMOS-Approach:

Comparison, how tensile stresses are treated in the various material laws

Benchmark calculations of lab tests and fieldconstellations

Evaluation of the relevancy of tensile stresses Damage development for a drift

at the WIPP-site

(Günther et al., 2015)




GmbH 19WEIMOS

WP 3: Deformation behavior resulting from tensile stresses Recalculation Brazilian Test

Lab test

Loading Rate Labor : 𝑣 =

1𝑚𝑚

100𝑠

Numerical simulation

Günther/Salzer Approach




GmbH 20WEIMOS


Work Packages



damage reduction






Till Popp (IfG)

Kai Herchen (TUC)

Andreas Hampel

presented by

Andreas Hampel

Till Popp (IfG)




GmbH 21WEIMOS

WP 2: Influence of temperature and stress state on damage reduction

Development of micro-cracks and progressive

damage at the opening contour (EDZ) after

excavation because of rock stress rearrange-

ments and the exceeding of the structural

strength boundary

Reduction of load bearing capacity and the

development of drift and shaft parallel by-

paths and secondary permeability

Knowledge of the damage reduction process

is important for the repository safety case

Motivation

leads to

therefore

Wall of an open driftSealing system / dam

Sketch of a repository

Shaft

Dam




GmbH 22WEIMOS

WP 2: Influence of temperature and stress state on damage reduction

Basic assumptions for the damage reduction process:

Long-term change in stress conditions in the near field of sealing

structures as a result of convergence process

Creeping of the rock salt mass on the sealing structure (hard

inclusion) / on the backfill material (soft inclusion) with increasing

contact pressure

Reduction of the damage and permeability development as a

result of crack closure and healing effects

WEIMOS-Approach:

Healing tests with different stress

states and temperatures

Qualification and improvement of

material models based on lab tests

=

1

*

1

*

11

12 113

1nn

h

vol

h

vol kknfs

F

fc

M

s

s

s

see

v

h MaaaMaa

aF s

= 8765

11

4 expexp1

nn

h kkQ

=

**

12 13

11

3

1

s

s

s

s

Simulation of a complex

model to demonstrate the

improved modeling

Approach

Stiff sealing

system

EDZ

Contact

pressure

Convergence

pressureGas- and liquid

tight rock salt mass




GmbH 23WEIMOS

WP 2: Influence of temperature and stress state on damage reduction TUC laboratory tests

4 Test machines

Sample size: 300/150 mm

V

EMC-System

30 MPa

2 MPa

29 MPa

1 M

Pa

/ m

in




GmbH 24WEIMOS

WP 2: Influence of temperature and stress state on damage reduction TUC lab test results

1. SeriesTemperature = 35°C Salt type: Asse

1st Test machine

Steel-dummy

Measurement of oil- and

test plant compressibility

Stopped for dilatancy

measurement with

immersion weighing

2nd Test machine

Salt sample

„Ass471“

4th Test machine

Salt sample

„Ass466“

3rd Test machine

Salt sample

„Ass470“

Stopped for dilatancy

measurement with

immersion weighing




GmbH 25WEIMOS

WP 2: Influence of temperature and stress state on damage reduction TUC lab test results

& further tests

3. Series2. Series

Str

ess (

MP

a)

Str

ess (

MP

a)

1. Series

Temperature = 35°C

Temperature = 60°C Temperature = 35°C

Axia

l str

ess s

igz

Confining

stress sigx,y

Axia

l str

ess s

igz

Confining

stress sigx,y




GmbH 26WEIMOS

WP 2: Influence of temperature and stress state on damage reduction Modified TUC healing test

Axia

l str

ain

(%)

Test characteristic

1

1

2

23

3 Loading path

Dilatancy strength

sDiff = 28 MPa

sDiff = 28 MPaDamage free

creep

Healing

Loading history

Damage induced

creep

Temperature = 35°C Dila

tan

cy

(%)

Ultra

sonic

wave

velo

city

(-)




GmbH 27WEIMOS



damage reduction







Till Popp (IfG)

Kai Herchen (TUC)

Till Popp (IfG)

Andreas Hampel

presented by

Andreas Hampel

Work Packages

Technology

10 Current status of research in the Joint Project WEIMOS