SatSensegroundmovementdataprovidesanoverviewofthegroundmovementaroundassetssuchasthoseusedinminingwithbenefitsincluding:

• mm/yearaccuracy• measurementpointsascloseas5metersapart• newmeasurementeverysixtotwelvedays• large,evenremoteareascontinuouslyupdated• dataimmediatelyavailablebetween2015topresentday• cansteermoreconventional,expensivein-situsurveyingtechniques

How does it work?SatSense uses radar data from Sentinel-1 satellites to create ground movement products. The orbit of the satellite allows us to update this data with a new measurement in time every 6-12 days everywhere. Our advanced, proprietary algorithms are built on the InSAR technique, and yield ground movement rates with mm/yr accuracy. The radar images have a resolution of 4 by 14 meters and can cover tens of thousands of square kilometres, making it uniquely suitable to monitor ground movements across a large range of spatial scales. SatSense currently pre-processes data over the United Kingdom, and is unique in its ability to keep data up-to-date in near-real time.

Our ground movement data is accessible instantly through the SatSense data portal. Data can also be downloaded in a format convenient to the user, for more detailed analysis locally. Convenient, instant access to the SatSense ground movement data allows geotechnical engineers, asset managers and decision makers to get an overview of both historic and current movements over their sites and the surroundings on a moment’s notice, facilitating and expediting informed decision-making on distribution and utilisation of more expensive and time consuming in-situ monitoring- saving time, instrumentation cost, man power and potential vandalism of equipment.

Cost-effective Mining Ground Stability Monitoring For mining applications using InSAR

On January 25, 2019, a tailings dam at the Córrego do Feijão iron ore mine, close to the town of Brumadinho, Brazil, collapsed catastrophically. This released a toxic mud flow, killing over 250 people [1][2]. Figure 1 below shows satellite images taken before and after the dam collapse, showing the destruction in the immediate vicinity. To determine if there were preliminary movements visible on the collapsed dam, SatSense processed data going back to early summer 2015, see Figure 2 below. The coloured points that overlay the aerial photograph show the average rate of movement at those locations. The mine itself, including the tailings dam, are well covered by measurement points, as opposed to the challenging forested area surrounding the mine. A distinct subsidence signal, as indicated by the red points, can be seen on the tailings dam, clearly showing that there were movements detectable prior to the collapse.

Average ground movement rates only reveal part of the story. Every measurement point also has a complete time history, revealing variations of movement behaviour over time. The time history for one of the points on the dam is shown next to the overview map. It reveals multiple slipping events, starting two years before the collapse. In the weeks before the collapse, the onset of the catastrophic slip can be seen clearly as well. The Brumadinho dam is an example of the value InSAR adds to mining operations monitoring. Significant movements on the tailings dam were visible in the data, and could have triggered closer inspection, increased in-situ monitoring and preventative maintenance action. A massive ecological and social disaster could have been averted, while also saving the mining company large sums of money [3]. InSAR provides large scale monitoring of entire sites and their surroundings, a cost-effective way to obtain an overview of ground movements, allowing strategic decision-making regarding deployment of in-situ monitoring methods and operations.

Figure1 Figure2

Aerial photographs showing the area around the collapsed tailings dam at Córrego do Feijão iron ore mine, Brazil. The brown dotted lines show the location of the top of the dam, with the toxic sludge lake in the top left of the scene. The collapse of dam caused a toxic mudflow, which can be clearly seen in the aerial photograph after the event. Over 250 people lost their lives in this event, with the ecological damage still unknown. Aerial photographs from Bing Maps (before) and Google Maps (after).

SatSense measurements over the collapsed tailings dam. The coloured points on the aerial photograph shows the average movement rate of each measurement point between May 2015 and January 2019. Red points denote subsidence, clearly showing an area of subsidence in the centre section of the dam. The time history for one of the subsiding points on the dam, indicated by the black arrow, is also shown. It clearly shows three episodes of slip on the dam, starting in November 2016, November 2017 and November 2018. The final episode culminated in the collapse of the dam in January 2019.

References

[1] https://www.reuters.com/article/us-vale-sa-disaster-exclusive/exclusive-brazil-prosecutor-aims-to-charge-vale-within-days-over-mining-waste-dam-disaster-idUSKBN1Z72GS [2] https://www.youtube. com/ watch?v=sKZUZQytads [3] https://www.ft.com/content/8c2f26f6-72b0-11e9-bf5c-6eeb837566c5

Cost-effective Mining Ground Stability Monitoring For mining applications using InSAR

Movement

Brazil mining example