Monitoring active open-pit mine stability in the Rhenish coalfields of Germany using a coherence-based SBAS method

With the recent progress in synthetic aperture radar (SAR) technology, especially the new generation of SAR satellites (Sentinel-1 and TerraSAR-X), our ability to assess slope stability in open-pit mines has significantly improved. The main objective of this work is to map ground displacement and slope instability over three open-pit mines, namely, Hambach, Garzweiler and Inden, in the Rhenish coalfields of Germany to provide long-term monitoring solutions for open-pit mining operations and their surroundings. Three SAR datasets, including Sentinel-1A data in ascending and descending orbits and TerraSAR-X data in a descending orbit, were processed by a modified small baseline subset (SBAS) algorithm, called coherence-based SBAS, to retrieve ground displacement related to the three open-pit mines and their surroundings. Despite the continuously changing topography over these active open-pit mines, the small perpendicular baselines of both Sentinel-1A and TerraSAR-X data were not affected by DEM errors and hence could yield accurate estimates of surface displacement. Significant land subsidence was observed over reclaimed areas, with rates exceeding 500 mm/yr, 380 mm/yr, and 310 mm/yr for the Hambach, Garzweiler and Inden mine, respectively. The compaction process of waste materials is the main contributor to land subsidence. Land uplift was found over the areas near the active working parts of the mines, which was probably due to excavation activities. Horizontal displacement retrieved from the combination of ascending and descending data was analysed, revealing an eastward movement with a maximum rate of ∼120 mm/yr on the western flank and a westward movement with a maximum rate of ∼ 60 mm/yr on the eastern flank of the pit. Former open-pit mines Fortuna-Garsdorf and Berghein in the eastern part of Rhenish coalfields, already reclaimed for agriculture, also show subsidence, at locations reaching 150 mm/yr. The interferometric results were compared, whenever possible, with groundwater information to analyse the possible reasons for ground deformation over the mines and their surroundings

A-DInSAR technique applied to the surface displacements of the GW sector of the Brucutu mine – Quadrilátero Ferrífero

A mina de Brucutu encontra-se na porção nordeste do Quadrilátero Ferrífero, no município de São Gonçalo do Rio Abaixo, a aproximadamente 120 km a leste de Belo Horizonte, Minas Gerais. Nesse local, a empresa Vale S.A. opera uma das maiores minas de ferro do Brasil. O minério de ferro encontra-se alojado nos itabiritos e em corpos de hematita da Formação Cauê. Essas rochas têm diferentes comportamentos geomecânicos, visto que elas ocorrem em contatos com rochas intrusivas e encontram-se brechadas, intensamente foliadas e fortemente intemperizadas. Os taludes das cotas 1.030 a 1.000 m, do setor GW da cava de Brucutu, vem registrando instabilidades nos últimos anos. O presente estudo visou analisar os deslocamentos superficiais e discutir os prováveis fatores controladores. Utilizou-se a técnica Advanced Differential Radar Interferometry (A-DInSAR) a partir de imagens do sensor COSMO-SkyMed em modo StripMap para monitorar os deslocamentos. Os períodos abrangidos para o desenvolvimento do presente trabalho foram de junho de 2018 a agosto de 2019 e de junho de 2019 a novembro de 2020. As imagens utilizadas foram fornecidas e processadas pela empresa Telespazio Brasil. Foram utilizadas também ortoimagens provenientes de Aeronave Remotamente Pilotada (ARP), dados geológicos-geotécnicos de campo e dados pluviométricos. Os resultados obtidos por meio do monitoramento A-DInSAR mostram que foram identificadas taxas de deslocamento consideráveis (até -76,3 mm/ano) no período chuvoso. As instabilidades presentes na área de estudo são condicionadas pelos seguintes fatores: contato entre rochas intrusivas (IN) e itabirito friável (IF); atitude desfavorável da foliação; e índices pluviométricos elevados que produzem o desmantelamento (erosão) da face dos taludes.The Brucutu mine is in the northeast portion of the Quadrilátero Ferrífero, in the municipality of São Gonçalo do Rio Abaixo, approximately 120 km east of Belo Horizonte, Minas Gerais. In this place, Vale S.A. operates one of the largest iron ore mines in Brazil. Iron ore is housed in itabirite and hematite bodies of the Cauê Formation. These rocks have different geomechanical behaviors, since they occur in contact with intrusive rocks and are breached, intensely foliated and strongly weathered. The slopes of the quotas 1,030 to 1,000, of the GW sector of the Brucutu pit, have been registering instabilities in recent years. The present study aimed to analyze the superficial displacements and discuss the probable controlling factors. The Advanced Differential Radar Interferometry (A-DInSAR) technique was used from images of the COSMO-SkyMed sensor in StripMap mode to monitor the displacements. The periods covered for the development of this work were from June 2018 to August 2019 and from June 2019 to November 2020. The images used were provided and processed by the company Telespazio Brasil. Orthoimages from Remotely Piloted Aircraft (RPA), field geological-geotechnical data, and rainfall data were also used. The results obtained through A-DInSAR monitoring show that considerable displacement rates (up to -76.3 mm/year) were identified in the rainy season. The instabilities present in the study area are conditioned by the following factors: contact between intrusive rocks (IN) and friable itabirite (FI); unfavorable attitude of foliation; and high rainfall rates that produce the dismantling (erosion) of the slope face.&nbsp

Técnica A-DInSAR aplicada aos deslocamentos superficiais do setor GW da mina de Brucutu – Quadrilátero Ferrífero

A mina de Brucutu encontra-se na porção nordeste do Quadrilátero Ferrífero, no município de São Gonçalo do Rio Abaixo, a aproximadamente 120 km a leste de Belo Horizonte, Minas Gerais. Nesse local, a empresa Vale S.A. opera uma das maiores minas de ferro do Brasil. O minério de ferro encontra-se alojado nos itabiritos e em corpos de hematita da Formação Cauê. Essas rochas têm diferentes comportamentos geomecânicos, visto que elas ocorrem em contatos com rochas intrusivas e encontram-se brechadas, intensamente foliadas e fortemente intemperizadas. Os taludes das cotas 1.030 a 1.000 m, do setor GW da cava de Brucutu, vem registrando instabilidades nos últimos anos. O presente estudo visou analisar os deslocamentos superficiais e discutir os prováveis fatores controladores. Utilizou-se a técnica Advanced Differential Radar Interferometry (A-DInSAR) a partir de imagens do sensor COSMO-SkyMed em modo StripMap para monitorar os deslocamentos. Os períodos abrangidos para o desenvolvimento do presente trabalho foram de junho de 2018 a agosto de 2019 e de junho de 2019 a novembro de 2020. As imagens utilizadas foram fornecidas e processadas pela empresa Telespazio Brasil. Foram utilizadas também ortoimagens provenientes de Aeronave Remotamente Pilotada (ARP), dados geológicos-geotécnicos de campo e dados pluviométricos. Os resultados obtidos por meio do monitoramento A-DInSAR mostram que foram identificadas taxas de deslocamento consideráveis (até -76,3 mm/ano) no período chuvoso. As instabilidades presentes na área de estudo são condicionadas pelos seguintes fatores: contato entre rochas intrusivas (IN) e itabirito friável (IF); atitude desfavorável da foliação; e índices pluviométricos elevados que produzem o desmantelamento (erosão) da face dos taludes

An investigation of ongoing displacements of active faults in the Gobi desert using persistent scatterer interferometric synthetic aperture radar technique to support the permanent disposal of high-level waste in Beishan, China

This research demonstrated the application of PSInSAR method in identifying and characterising the micro-displacements along active faults in Beishan to support the selection of GDF host rock. This research first distinguishes and separates the tectonic induced and non-tectonic induced deformation within three study areas at Suanjingzi, Jiujing and Xinchang. Through the application of coherence change detection, it found the granite outcrop areas characterised by high coherence provide more robust results of tectonic activity. The Quaternary sediments covered areas which are characterised by low coherence usually show higher deformation rates due to the impacts of erosion and deposition. The tectonic induced displacements generally range from -0.4 to 0.4 mma-1 and are dominated by fault bound tectonic movements. As a part of wrench faut zone, Beishan is impacted by a NE-SW trended maximum in situ compressive stress field (σ1). To correlate the visible valleys, gullies, or cracks in Google Earth imagery with the SAR image deformation discontinuities, this study mapped and characterised more than 40 active faults in the three study areas, these include (1) the NE-SW trended sinistral strike-slip faults triggered by extension and (2) the NW-SE/W-E trended reverse faults triggered by maximum compression. The fault activity is characterised by subtle (minor) displacement rate value difference between the two sides of the fault plane. This research successfully improved the understanding of local structural geology and provided moderate guidance for the selection of HLW disposal sites in China. It was indicated that Xinchang has the highest tectonic stability, and this is then followed by Jiujing and Suanjingzi. This kind of displacement rate difference is possible due to the angle difference towards the Sanweishan Fault Zone. To trace and characterise the undiscovered active fault planes, the PSInSAR approach also benefits the prediction of earthquake by improving the positioning of the potential epicentres.Open Acces

Book of short Abstracts of the 11th International Symposium on Digital Earth

The Booklet is a collection of accepted short abstracts of the ISDE11 Symposium

Detection and Monitoring of Surface Motions in Active Open Pit Iron Mine in the Amazon Region, Using Persistent Scatterer Interferometry with TerraSAR-X Satellite Data

Persistent Scatterer interferometry (PSI) represents a powerful tool for the detection and monitoring of tiny surface deformations in vast areas, allowing a better understanding of its triggering mechanisms, planning of mitigation measures, as well as to find better solutions for social and environmental issues. However, there is no record hitherto of its use in active open pit mine in tropical rainforest environment. In this paper we evaluate the use of the PSI technique for the detection and monitoring of mine slope deformations in the N4W iron mine and its surroundings, Pará State, Northern Brazil. The PSI processing was performed with 18 ascending SAR scenes of the TerraSAR-X satellite acquired in the dry season of 2012. The results showed a significant number of widely distributed persistent scatterers. It was observed that most of the study area was stable during the time span. Nevertheless, high deformation rates (312 mm/year) were mapped over the mine waste piles, but do not offer any hazard, since they are expected displacements of meters in magnitude for these manmade land structures. Additionally, it was mapped tiny deformation rates in both the east and west flanks of pits 1 and 2. The main underlying reasons can be assigned to the accommodation phenomena of very poor rock masses, to the local geometric variations of the slope cuts, to the geological contact between ironstones and the country rocks, to the exploitation activities, as well as to the major geological structures. This study showed the applicability of the PSI technique using TerraSAR-X scenes in active open pit mines in tropical moist environment. However, the PSI technique is not capable in providing real-time warnings, and faces limitations due to SAR viewing geometry. In this sense, we strongly recommend the use of radar scenes acquired in both ascending and descending orbits, which would also provide a more complete understanding of the deformation patterns