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”?