12-01 slope monitoring methods
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1
Grasberg, 2003
Slope Monitoring
Types of slope instruments
Displacement monitoring devicesPrecise surveysDifferential global positioning systems (DGPS)Space-borne and terrestrial SAR Interferometry
Strain monitoring devicesSurface extensometersBorehole extensometersBorehole inclinometersTiltmetersTime domain reflectometry (TDR)
Pore-pressure measurementsPiezometers and monitoring wellsTensiometersTDR moisture gauges
MicroseismicityGeophones
2
Displacement monitoring1) “Total Station”: Electronic Distance Measurement
(“EDM”) + Theodolite
2) “DGPS” Differential Global Positioning System:Base station+measuring stations Target prism
Britannia Mine, B.C. Disturbed Area
PR #104
PR #102
PR #100
3
PR #100
PR #104
PR #102
“East Block”
East Block, failure model
0 50 100 150 200 250 300 350 400
1000
1050
1100
1150
1200
1250
1300
1350
1400
ELE
VA
TIO
N (m
)
Toppling(schematic)
Tensioncracks
102
100
300,000 m3
0 50 100 150 200 250 300 350 400
1000
1050
1100
1150
1200
1250
1300
1350
1400
ELE
VA
TIO
N (m
)
Toppling(schematic)
Tensioncracks
102
100
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MonitoringJane Basin Slope
26-Jul-02 30-Aug-04
04-Jan-9506-Jan-92
05-Aug-93
25-Nov-92
20-Jul-92
-0.15
-0.10
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
Jan-92 Jan-93 Jan-94 Jan-95 Jan-96 Jan-97 Jan-98 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06
Date
Del
ta T
otal
Mov
emen
t (m
)PR100
PR101
PR102
PR103
PR104
Coal Mine Waste Dumps
5
Wire extensometer
With data logger
Borehole extensometer (Slope Indicator, Ltd.)
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Surface rod extensometer (“crackmeter”)
Vibrating wire displacement gauge (or a vernier for manual readings or a linear transducer) accuracy <1mm
Tape extensometer
Rod Extensometers
ISMES, Valtellina, Italy
ETH, Switzerland
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Borehole inclinometer (“Slope Indicator”)
Some inclinometer applications (Slope Indicator, Ltd.)
8
Time domain reflectometry (TDR)
Synthetic aperture radar interferometry (SAR)
9
Piezometers
▼ 1) Observation well (open) –not a piezometer
2) Pneumatic piezometer
3) Standipe(Casagrande) piezometer
4) Electric piezometer(Vibrating Wire)
SEAL
SAND PACK
MEMBRANE
AIR
Piezometercomparison
10
Slope Indicator multi-point vibrating wire
piezometer
Grasberg, 2003
Monitoring Interpretation
11
Chuquicamata Mine, Chile, 1968
Movement vector F-2
Micro-seismic events/day
Chuquicamata Mine, Chile, 1968
Movement vector F-2
Micro-seismic events/day
12
Inverse Velocity Method (Fukuzono, 1985)Normal
Inverse
Inverse Velocity Method, more examples
“La Clapiere”France
PredictionReal
Tripp Mine: slow failure
13
Inverse Velocity Method, another example
18-Jul-01 25-Jul-01 1-Aug-01 8-Aug-01 15-Aug-01 22-Aug-01 29-Aug-01DATE
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
INV
ER
SE
VE
LOC
ITY
(day
s/cm
)
45 40 35 30 25 20 15 10 5 0TIME BEFORE FAILURE (DAYS)
0
5
10
15
20
25
30
35
VE
LOC
ITY
(cm
/day
)45 40 35 30 25 20 15 10 5 0
TIME BEFORE FAILURE (DAYS)
Regression coeffiecient (R2) = 99%for all inverse-velocity fits
Predicted velocity curves (basedon inverse-velocity fits) comparedwith actual velocity data
18 million m3 pit slope failure prediction (Rose and Hungr, 2006)
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Use of inverse velocity to monitor stabilization progress (Rose and Hungr, 2006)
1-May-02 16-May-02 31-May-02 15-Jun-02 30-Jun-02 16-Jul-02 31-Jul-02 15-Aug-02DATE
0
0.5
1
1.5
2
INV
ER
SE
VE
LOC
ITY
(day
s/cm
)
105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 25 20 15 10 5 0TIME BEFORE FAILURE (DAYS)
Buttress and OffloadRemedial Measures
Stabilization of Slope Displacements
Regression Coeffiecient (R2) = 96 to 99%for all Inverse-Velocity Fits.
Pats FaultMidnight Fault
Carlin waxy silt unit
100mScale
Two faults and a pre-sheared silt layer, 3 million m3
Total Displacement?
ValPola rock avalanche, 1986
100 m pre-historic movement
New crack
15
Small rock slides
Libby Dam, Montana, 1971
Prediction not feasible
Purpose of monitoring
1) Movement detection, failure prediction
2) Vector solutions, interpretation of failure mechanism
(Cruden, 1986)
Predicted rupture surface
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