Assessment of the Available Historic RADARSAT-2 Synthetic Aperture Radar Data Prior to the Manefay Slide at the Bingham Canyon Mine Using Modern InSAR Techniques

Abstract

In April 2013, Rio Tinto Kennecott Copper’s (RTKC) Bingham Canyon Mine experienced what is arguably the world’s largest ever in-pit slope failure. The failure initiated on the east wall of the mine, along major, continuous, low-strength bedding faults, which were the upper and lower contact of the Manefay hornfels bed. The failure comprised approximately 145 million tonnes of rock and waste dump material. East wall slope deformations were detected some months prior to the catastrophic slope collapse by RTKC’s ground-based slope monitoring systems. Use of existing terrestrial radar and prism monitoring systems provided excellent data to manage the response to the slope collapse. The failure resulted in no injuries/loss of life, although the failure runout distance was longer than expected, resulting in the loss of mining equipment and significant production interruption. Post-failure investigations identified an RTKC-sponsored, university research project, which detected a zone of sporadic ground deformation at the crest of the Manefay failure using satellite-based Interferometric Synthetic Aperture Radar (InSAR) monitoring. When the outcomes of this research study were received in 2010, RTKC responded by conducting detailed field inspections, installing prisms in the area of concern and monitoring the area closely in the years before the event. Interferometric methods for calculating ground displacement from satellite-based synthetic aperture radar (SAR) data have improved significantly since the time leading up to the Manefay failure. These updated methods have been used in this study of the available historic SAR data with results indicating that significant ground movements were occurring over a number of years prior to failure. Detailed knowledge of these movements could potentially have led to a different interpretation of failure mechanisms and magnitude and, in hindsight, different slope management and mine development plans in the years preceding slope failure. From a business and mine operations perspective, the ability to identify subtle signs of slope failure before a catastrophic slope collapse is essential for appropriate management of such events. The use of InSAR monitoring, as discussed in this paper, provides an increased capability for further improved slope management at RTKC, and at other mining operations.