golder associatescarter ppt
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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)
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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
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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
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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….
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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
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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
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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
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so …. Characterizing discontinuit ies
becomes key to Design
OTV ATVCALIPER
MECHANICAL &
TELEVIEWER
February 29, 2012 … thence becomes possible to Estimate Takes & Travel Distances
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Fracture Characterization Tools
February 29, 2012 9
Acoustic TeleViewer
Optical TeleViewer
3–Arm Caliper
Motor
Mirror
Bellows
(oil filled)
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Analyzing Televiewer Data
February 29, 2012 10
“ UNWRAPPED”
OPTICAL TELEVIEWER
IMAGE
N NS WE
PLANE SLICE
THROUGH A
CYLINDER
N
EW
S
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Definition of Fracture Geometry
11
February 29, 2012
(a) All Fractures (except bedding) (b) Subvertical Jointing (c) Shear features (25-75 dip)
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Example – Fracture Data from ATV
February 29, 2012 12
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 )
<
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Example – Distribution of Lugeon Data
February 29, 2012 13
“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
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Correlate – Hydraulic and Aperture Data
February 29, 2012 14
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
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Example – Portugués Dam
February 29, 2012 15
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
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Fracture roughness affects penetration of
grout into fractures
February 29, 2012 16
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
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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)
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Understanding Fracture Roughness also matters when
choosing the right grout to ensure pressure build…
Conglomerate roughness is purple line; Limestone roughness is blue line
February 29, 2012 18
• 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
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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
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Evaluate Effectiveness of Grouting
February 29, 2012 20
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%
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Grouted Fracture Set
visualized in
Time Step through injection within “Sequence” screen
0
Injection Time
1000+ Steps
Grouthole
Simulated Injection into Fracture Network
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Visualized to evaluate “ Penetration”
0.0m
Distance
10.0m
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I N T E N S I T Y
So what’s new? … the implementation approach …
February 29, 2012 23
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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