3vG conducted an InSAR historical analysis on an open pit mine and associated tailings facilities for a North American mine. The primary objective of the analysis was to create a complete database of moving areas in and around the site, regardless of slope topography.
Significant topography in and around the mine
InSAR is only sensitive to line of sight motion
Areas of potential interest are on both east and west facing slopes
Solution & Results
3vG analyzed 57 images taken over 16 months by the TerraSAR-X satellite. Of these images, 29 were taken when the satellite was looking east and 28 when the satellite was looking west. While a particular look direction may have limited sensitivity to certain slopes, due to motion along the slope being perpendicular to the satellite line of sight or the slope not being visible to the satellite, the other look direction almost always has good sensitivity to displacement along that slope. By combining the data from two different look directions, 3vG was able to obtain complete coverage over the mine site. With this dual-look processing, 3vG was also able to derive the direction of displacement for all points measured with both look directions.
Significant displacement approaching 25 cm/year was detected in the main pit and multiple slopes in the immediate vicinity of the main pit were also found to be moving at rates greater than 5 cm/year. While parts of the tailings facilities were found to be sinking at 20 cm/year, the tailing’s dam wall was found to be stable, with no significant displacement detected along the dam wall.
Line of sight derived displacement rates from east looking (left) and west looking (middle) datasets. (Right) The displacement rate derived by combining the data with purple lines denoting areas of confirmed motion. The west looking data clearly detects displacement on west-facing slopes that the east looking data is insensitive to and vice versa. North is at the top of the figures.
Line of sight derived displacement rates from east looking (left) and west looking (right) data sets. For this slope of the pit, the west looking data is not sensitive to motion while the east looking data clearly delineates the edge of the motion area.
Region of confirmed displacement highlighted with the purple contour (left) and the derived displacement rate (right) over the optical image of the region. This analysis has clearly detected a locally unstable slope along the edge of the mine site undergoing subsidence.
While the tailings facilities show some subsidence, the displacement wall shows no sign of displacement. The optical image is shown on the left and the InSAR derived rate is shown on the right. The purple contour shows the region of confirmed motion.
Dual-look processing provides complete coverage of a mine site, allowing for identification of movement zones on both east and west facing slopes
Dual-look processing provides the direction of motion thereby increasing the accuracy of the determination of the total magnitude of the motion
Coverage of entire mine sites, including outlying areas such as tailings facilities in a single analysis
3vG’s advanced multi-look processing tools provides complete coverage of large mine sites, allowing for the detection and subsequent monitoring of active motion areas anywhere in the site.