Transcript - Large Open Pit

EXPERIENCES WITH
RADAR MONITORING
Is radar as good as some
people believe?
LOP April 2014
Radar for slope monitoring
• Industry utilization – sampling
~420 radars = 223 GP + 108 Reutech + 90(+) IDS
Anglo = 60+
Newmont = 10
Barrick = 15
Rio Tinto = 30
Freeport = 50
DeBeers = 5
Debswana = 15
Kinross = 7
Teck = 7
BHPB = 19+
• Probably more than half of radars with LOP sponsors
• Is the market big enough for more players?
• Would quality (product and/or service) suffer in a flooded market?
ILLUSTRATIVE CASE
HISTORIES
Comparison of RTS Total
Movement with Radar Monitoring
KCGM
Batu Hijau
Observations of Trimble RTS
prism survey trends (total
movement) vs IBIS radar surveys
of the east highwall at the KCGM
mine; Kalgoorlie, WA
View of KCGM’s open pit in early November 2013 looking northward; the completed
Trafalgar cut east highwall is in shadow.
IBIS radar image of relative movement on the east highwall of the KCGM open pit;
colors in the image indicate relative movement rates, where the highest rate of
movement is at the toe of the recently completed Trafalgar Cut. A small yellow
patch on the left side of the figure marks the location of the IBIS radar.
Reference prism selected by IDS to determine total movement
representative of the “small reference” window they chose to hold stable for
analysis of main movement areas indicated by the colored regions of the
IBIS image.
Note: we could do better to maintain RTS surveys; tendency to get lazy about this
when we have radar in place; data gap is due to mining and RTS relocation
TR210_08 (moving area)
60
y = 0.1423x - 5850.7
50
40
30
20
10
y = 0.0628x - 2584.3
0
-10
Trimble
IBIS Large Areas
IBIS Small Areas
Linear (Trimble)
Linear (IBIS Small Areas)
Blast event
Results and Recommendations by KCGM
• Assessments by KCGM and IDS appear to be complementary, and we can confirm
that we have reliable cross-validated Trimble and IBIS survey data;
• Radar detected movement accounts for only 33% total movement (Trimble) in midslope (Area 3); (angular difference between average total vector direction and IBIS
LOS is ~30-40°, so you might expect IBIS to pick up 75-85% of total LOS
movement)
• The “stable reference” used by IDS is moving, interpreted to be normal mining
induced deformation;
• Radar surveys should be considered to be a record of relative movement only,
where the stable reference window is assumed to be stationary;
KCGM Results (Cont.)
• Prism surveys are a measure of absolute movement, assuming the RTS
survey pillar is stationary (important to ensure correct (1st Order) reference
control; best when using two RTS with several common back-sites and
robust theodolite pedestal movement checks) ; the Trimble survey results
should therefore be used for numerical model calibration;
• Radar surveys are useful for safety monitoring of critical slope
performance; but should be recognized that radar may be capturing
significantly less of the total movement than we think;
• Movement rates are highest where there has been recent mining and
decrease with time (regressive), unless there is instability;
• Permanent deformation on 03 Sept. measured from IBIS data is attributed
to a -600 RL blast = 2 mm in Area 1; and 0.6 mm in Area 2; actual
permanent displacement may be significantly more than that measured by
radar.
Batu Hijau
Note that this mine has recently
been very successful in managing
instabilities using radar
Example from Batu Hijau
Comparing MSR radar and Leica/GeoMOS surveys
CASE HISTORY CONCLUSIONS
• Radar is capable of very accurate
measurements, but the movements must
be treated as “relative”
• Because the radar may only be detecting
a fraction of the total movement, as well as
the LOS limitation, it may not be the best
indicator of the onset of instability
• Interpretation of radar data requires very
well trained and experienced operators
Manufacturers’ Battles
Should operators be concerned?
Comparing Real Beam and Synthetic Aperture Techniques for Slope Stability Radar;
White Paper C1001; Prof. I.D. Longstaff, UQ, Australia; 2011
Counterpoint to Prof. Longstaff’s White Paper
•
•
From: IBIS vs Competitors; IDS Presentation; 2014.
See also: Real Beam vs. Synthetic Aperture Radar for Slope Monitoring; Massimiliano Pieraccini; Progress
in Electromagnetics Research Symposium Proceedings, Stockholm; Aug. 2013.
EXPERIENCE IN COLD WEATHER
OPERATIONS
• Based on a survey of selected LOP
sponsors:
1) IBIS units appear to work well. Most, but not all, are in
Seacan containers with scene windows. Some, again
but not all, are heated.
2) One Reutech MSR-300 is working well in the cold, with
cold weather kit.
3) SSRs seem to give problems, even when equipped with
cold weather kits. However, several of those are “old”.
MORE APPLICATIONS FOR RADAR?
•
•
•
•
Blast deformation monitoring/assessment
Mobility improvements
Rapid assessment (CGG a new player)
Integrated deformation assessment (e.g., HMI
from Reutech – next slide)
Utilization of Reutech’s HMI software at
Gold Quarry to capture LOS prism data to
compare with radar measured movement
in the same area.
Green line is Geomos (Leica) LOS
survey, for direct comparison to radar
survey (red)
Note: prism data imported from GeoMOS, but can
also import Trimble and Quikslope
Geo-referencing experience with
GroundProbe?
• Does anyone have similar experience to
share using SSRs, such as for time vs
displacement trend analysis?
• Is there experience using SSR georeferencing to show prism locations and
comparative trends?
For Discussion
• Any other experience in quantifying radar measured
movement vs total vector from prisms? Does it matter?
• Similar or other observations of limitations of all radar
systems; or specific systems?
• Opinions regarding utilization of one radar system over
another for safety critical monitoring, vs surveillance?
• Should numerical models be calibrated using radar
data?
• Relevant experience using LiDAR, or photogrammetry?
• Should the LOP develop their own “White Paper”?