12-01 Slope monitoring...
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Grasberg, 2003 Slope Monitoring Types of slope instruments Displacement monitoring devices Precise surveys Differential global positioning systems (DGPS) Space-borne and terrestrial SAR Interferometry Strain monitoring devices Surface extensometers Borehole extensometers Borehole inclinometers Tiltmeters Time domain reflectometry (TDR) Pore-pressure measurements Piezometers and monitoring wells Tensiometers TDR moisture gauges Microseismicity Geophones
Transcript of 12-01 Slope monitoring...
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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
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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
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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
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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.)
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Time domain reflectometry (TDR)
Synthetic aperture radar interferometry (SAR)
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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
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Slope Indicator multi-point vibrating wire
piezometer
Grasberg, 2003
Monitoring Interpretation
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Chuquicamata Mine, Chile, 1968
Movement vector F-2
Micro-seismic events/day
Chuquicamata Mine, Chile, 1968
Movement vector F-2
Micro-seismic events/day
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Inverse Velocity Method (Fukuzono, 1985)Normal
Inverse
Inverse Velocity Method, more examples
“La Clapiere”France
PredictionReal
Tripp Mine: slow failure
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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
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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
