golder associatescarter ppt

8/17/2019 Golder AssociatesCarter PPT

1/23

Improved Methods of Design for

Grouting Fractured Rock

Presented by: Trevor Carter

February 17, 2012

Trevor G. Carter 1, William Dershowitz2, Dawn Shuttle2 and Michael Jefferies3

1, 2 & 3 Golder Associates Toronto, Seattle & Vancouver

Companion paper to:

“Towards BetterInjection Control and

Verification

of Rock Grouting”

Bonin et.al. (2012proceedings)


2/23

Concept of … Aperture Controlled Grouting

New Concept – or is it?

Lets start with an Assumption? (or is it a Fact?)

Grout Takes are Controlled by Fractures

Basis of Concept …. Definition of Fracture Characteristics is central to design

Concept tenet that understanding fracturing is key to:

specifying grout rheology & take “targets”;

establishing “grouting effectiveness”; and

developing Grouting Protocols – hole spacing, mix thickening

sequences and volume cut-offs

So what is “ Aperture Controlled Grouting” (ACG)?

Nothing New really:perhaps best thought of ……as a blend of ….

the best of GIN (pressure control) procedures,plus

the best of (viscosity increase) Aussie Approach


3/23

Basics of Concept …. presented in 1982

Ref . Carter, 1982, Jefferies et al, 1982,

Rogers et al, 1982papers on initial use of electronic monitoring;

same basic data collection as today


4/23

Basics of Concept …. presented in 1982

4

Ref . Carter, 1982, Jefferies et al, 1982,

Rogers et al, 1982papers on initial use of electronic monitoring;

same basic data collection as today

GROUT INTENSITY

L U G E O N S

LUGEONS

G R O U T I N T E N S I T Y

Recognized different

Lugeon Behaviour of Water

Pressure Data & Grout Data

at different takes

chart in paper….


5/23

Conduct 5stage Lugeon

Water Test

Measure Apertures with

ATV

Match theDistributions

Develop a“matched”

Grout

Inject toVolume –PressureProtocolDetermine

Travel Distanceper Stage,based on

Lugeon & Take

DetermineEquivalent SingleFracture Aperturebased on LugeonValue & Take Data

Determine Individual Aperture by correct ing ATV

Aperture on prorata basisper individual fracture to

determine HydraulicFracture Apertures =

apertures / # fracs

Determine travel distance peraperture on prorata basis per

individual fracture to determineHydraulic Fracture Apertures = Frac

Aperture x ( apertures / # fracs)

Correct aperture & traveldistance on basis of

matching sum of fracture

disk volumes compared toactual stage take volume

Iterative “ Design” Flowsheet

In a nutshell…

February 29, 2012 5

21

3

4

67

9

10

8 5


6/23

Conduct 5stage Lugeon

Water Test

Measure Apertures with

ATV

Match theDistributions

Develop a“matched”

Grout

Inject toVolume –PressureProtocolDetermine

Travel Distanceper Stage,based on

Lugeon & Take

DetermineEquivalent SingleFracture Aperturebased on LugeonValue & Take Data

Determine Individual Aperture by correct ing ATV

Aperture on prorata basisper individual fracture to

determine HydraulicFracture Apertures =

apertures / # fracs

Determine travel distance peraperture on prorata basis per

individual fracture to determineHydraulic Fracture Apertures = Frac

Aperture x ( apertures / # fracs)

Correct aperture & traveldistance on basis of

matching sum of fracture

disk volumes compared toactual stage take volume

Iterative “ Design” Flowsheet

In a nutshell…

February 29, 2012 6

21

3

4

67

9

10

8 5


7/23

Fracture Characterization – Geologic Aspects

Need to DEFINE:

Fracture Spatial Pattern; Fracture Fabric & Number of Sets; and

Fracture Extent

February 29, 2012 7

> 1e-2 m2/sec

< 1e-10 m2/sec F r a c t u r

e t r a n s m i s s i v i t y : m 2 / s e c

1e-4 m2/sec

1e-6 m2/sec

1e-8 m2/sec


8/23

so …. Characterizing discontinuit ies

becomes key to Design

OTV ATVCALIPER

MECHANICAL &

TELEVIEWER

February 29, 2012 … thence becomes possible to Estimate Takes & Travel Distances


9/23

Fracture Characterization Tools

February 29, 2012 9

Acoustic TeleViewer

Optical TeleViewer

3–Arm Caliper

Motor

Mirror

Bellows

(oil filled)


10/23

Analyzing Televiewer Data

February 29, 2012 10

“ UNWRAPPED”

OPTICAL TELEVIEWER

IMAGE

N NS WE

PLANE SLICE

THROUGH A

CYLINDER

N

EW

S


11/23

Definition of Fracture Geometry

11

February 29, 2012

(a) All Fractures (except bedding) (b) Subvertical Jointing (c) Shear features (25-75 dip)


12/23

Example – Fracture Data from ATV


0

100

200

300

400

500

600

700

1 2 3 5 1 0

2 0

3 0

5 0

1

0 0

2

0 0

3

0 0

5

0 0

1 0 0 0

2 0 0 0

Aperture: mm (Note Log Scale )

F r e q u e n c y

( # o

f d i s c o n t i n u i t i e s )

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Frequency

Cumulative %

“Tight”

Features

Mean Fracture

Aperture

Aperture: mm (Note Log Scale)

F r e q u e n c y ( #

o f d i s c o n t i n u i t i e s )

<


13/23

Example – Distribution of Lugeon Data


“Tight”

Features

Lugeons (Log Scale) F

r e q u e n c y ( # o f W a t e r P r e s s u

r e T e s t s

Mean

Lugeon


14/23

Correlate – Hydraulic and Aperture Data


C D F

Fracture Aperture: m

T (m2 -7 x uL x Length (m)

“ T i g h t f e a t u r e s ”

Cross-plot

Lugeon Transmissivity

& Aperture Distributions


15/23

Example – Portugués Dam


Space one is trying to fillThis Aperture contro ls Optimum Grout

- particle size & rheology

This

aperture

controls

injection

pressure

Fracture transmissivity: m2/sec

F r a c t u r e

a p e r t u r e : m

m

Void-filling aperture

Hydraulic aperture

Different Curves for everySite & Rock Type -

Fracture Dependent


16/23

Fracture roughness affects penetration of

grout into fractures


Conglomerate fracture roughness Limestone fracture roughness

Same 30 uL grout stage… Same Rheology grout…

T R A V E L D I S T

A N C E

GROUT INTENSITY

(TAKE) LITRES/METRE


17/23

February 29, 2012

“ Take” & Conductivity influence Travel

T R A V E L

D I S T A N C E

GROUT INTENSITY

LUGEON CURVES

“ Take” = Intensity (Litres/metre)


18/23

Understanding Fracture Roughness also matters when

choosing the right grout to ensure pressure build…

Conglomerate roughness is purple line; Limestone roughness is blue line


• Same 30 uL

grout stage

• Same rheology

grout “Mix B”36 Second Marsh

GROUT INTENSITY

P E N E T

R A B I L I T Y

OK – will probably achieve

adequate closure

Problematic – so need

thicker formulation


19/23

Efficiency of Grouting – can be checked

February 29, 2012

Use Bingham model to approximate

grout flow

Model within DFN representation

Inject to proposed Grouting Intensity Check/simulate groundwater flow thru

curtain

Rerun to optimize – hole spacing etc

Aperture: mm

Travel Distance: m

D e p t h : m


20/23

Evaluate Effectiveness of Grouting


0.0

0.2

0.4

0.6

0.8

1.0

0.1 1 10

G r o u t i n g E f f i c i e n c y ( - )

Normalized Grouting Intensity: Vsimulated/ Voptimum (-)

Normalized Grouting Intensity

G r o u t i n g E f f i c i e n c

y

Grouting Efficiency: E = 1 – (KGrouted / Kformation)

Compute groundwater

flow across grout curtain

through remaining

ungrouted fractures in the

network

90%

Design Curve =

Optimum Volume

or Penetration

Distance

Twice

the effort

80%


21/23

Grouted Fracture Set

visualized in

Time Step through injection within “Sequence” screen

0

Injection Time

1000+ Steps

Grouthole

Simulated Injection into Fracture Network


22/23

Visualized to evaluate “ Penetration”

0.0m

Distance

10.0m


23/23

I N T E N S I T Y

So what’s new? … the implementation approach …


GIN Volume = GIN Factor / Mobilized Pressure

ACG Volume = Site (design) Factor * Stage Lugeon

Curve & equation transferred to site

staff for field implementation

Stage conductivity: Lugeon (uL)

R e q u i r e d G r o u t V o l u m e

( L e n g t h N o r m a l i z

e d ) : l t r / m )

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