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The end of hard coal mining in Germany and other European countries has been leading to new challenges in post-mining and utilisation of abandoned mines while opening up new perspectives concerning the remains of former mining as well as new fields of work for specialised personnel at the same time. Coping with the resulting perpetual tasks places new demands on already trained experts and offers the opportunity to familiarise the next generation of students with post-mining issues and solution approaches from the beginning. This article presents two closely interrelated projects – the USAMIN Project and the PepperMINT Project – which aim to successfully recruit and train future professionals. For this purpose, the USAMIN (USe of Abandoned MINes) Project creates a new form of distance learning as multilateral cooperation, which strengthens the training of specialised experts and the scientific exchange across European borders. Furthermore, the main goal of this project is the establishment of networks between scientists and other experts, thus strengthening international cooperation. The PepperMINT Project’s STEM online courses aim to motivate high school students to pursue STEM studies by introducing them to the field of engineering, while simultaneously strengthening students, especially in their first semesters. By linking the two projects, various actors can be connected according to their education and a large part of the education chain can be viewed in a holistic approach. [ABSTRACT FROM AUTHOR]

Mining of minerals impacts all components of the ecosystem and the post-mining environment should be continuously monitored to control the quality and efficiency of reclamation procedures. In the past post-mining areas often did not undergo the full process of reclamation and were left unmonitored. This study was aimed at analysis of surface (gully) erosion in an abandoned lignite post-mining area located in the present cross border German-Polish Geopark Muskau Arch. For this purpose, low-cost unmanned aerial vehicle (UAV) photogrammetry to acquire data describing the surface condition of partly rehabilitated dump sites and subsequently a digital elevation model (DEM) of difference (DoD) approach to analyse quantitatively elevation change were applied. The results based on processing of data from four UAV missions carried out between Spring 2020 and Autumn 2021 (18 months) allowed to determine the elevation models with high accuracy (±0.02 – ±0.04 m) and develop differential elevation models for the estimation of material movement and surface change in three selected gullies. All of the study sites were subjected to surface erosion probably due to the effect of rainfall that caused natural landscaping of the area. The greatest observed elevation changes connected with loss of material in research crosssections reached 0.9 m. The UAV based data calculation of the DEM of difference has proved a time efficient and accurate method for analysis of elevation change in post-mining areas subjected to surface erosion. For the best results it is recommended to plan the UAV flight missions when the sun is at its highest or in cloudy weather to minimise the effect of sunshading on the quality of the generated DEMs. A further study to correlate material movement with precipitation records is planned. [ABSTRACT FROM AUTHOR]

As part of the FloodRisk project, the influence of rising mine water in abandoned coal mines on induced seismicity is investigated. The Seismological Observatory of the Ruhr University Bochum operates a monitoring network for the whole Ruhr area (North Rhine-Westphalia, Germany) since 1983. The local scale FloodRisk network was installed in the eastern part of the Ruhr area in 2020. The continuous monitoring opens up the opportunity for a long-term study of seismicity in combination with water levels related to mining in the region. The resulting database for the eastern Ruhr area includes over 13,000 induced earthquakes in a period of 26 years during active mining, very few events in the postmining phase before the onset of flooding and more than 1,700 events in the first two and a half years of flooding. The seismological database is supplemented by the mine water levels, which are regularly measured at various measuring points distributed over the study dewatering area “Haus Aden” and made available by Ruhrkohle Aktiengesellschaft (RAG). Seismic activity was highest in the phase of active mining and concentrated in the vicinity of the mining areas. After the end of mining, only very low seismicity was detected. With the start of flooding, significantly more events were registered again. The rise curve of the mine water level and the temporal and spatial distribution of the seismicity are observed and analysed. Five temporal flooding phases are identified in which the correlated seismicity shows different distribution patterns. Phases in which the levels of individual sections of the mine merge in flooding show particularly high seismicity. A strong spatial clustering of well-localised events occurs below the deepest flooded levels of the mine. Several mechanisms that alter the stress in active mining and flooded mines and induce seismic events are known from previous studies. To apply this to our study, particular attention is given to the spatial distribution of seismicity in relation to known geologic and mining structures. In the flooding phase, most of the seismicity is localised in the area below the flooded drifts. [ABSTRACT FROM AUTHOR]

For the Research Centre of Post-Mining (FZN) at the Technische Hochschule Georg Agricola University (THGA) in Bochum, geomonitoring is a multi-level approach to environmental monitoring with a focus on post-mining activities. In situ, a precise understanding of natural processes, e.g. the condition of groundwater, water bodies, soil or vegetation, is developed – usually through mapping, laboratory analyses and installed sensors. The goal is to later be able to derive an areawide statement on these processes through the analysis of satellite data. In order to be able to transfer the process understanding gained to the satellite data, an unmanned aerial vehicle is used. This article highlights an essential aspect of the in situ component. The denser the coverage with sensors, the more reliably an area-wide statement about drones and satellites can succeed. This is why low-cost temperature and soil moisture sensors and loggers are also used in the FZN research projects. In the “Climate Change – Management and Monitoring (C2M2)” project, funded by the Emschergenossenschaft-Lippeverband (EGLV), such sensors could be evaluated in several tests. The article presents initial results aimed at mapping an annual cycle of soil moisture with such inexpensive sensors. As a result, no physically correct measurements can be achieved with these sensors, but they are able to show patterns in processes and, for example, map such annual cycles. With the appropriate interpretation, they can thus deliver a contribution to understand processes. [ABSTRACT FROM AUTHOR]

Mining of hard coal creates large underground cavities, which significantly affect the subsurface and land surface. Observations of land surface behaviour after the closure of mines demonstrate that these threats do not disappear. During mine water rebound in the post-mining phase of underground coalmines, the water flows into the open mine workings and other altered or fissured areas. This paper provides early observations from the PostMinQuake project, which is designed to identify mechanisms, relevant parameters and dependencies of mining and geological parameters causing post-mining seismicity in several European coal regions. It also presents the correlation between seismicity and water table level in the studied basins that has been observed during the post-mining phase and shows the necessity of implementing new procedures to monitor these seismic events. [ABSTRACT FROM AUTHOR]

The successive end of hard coal mining, which took place in the various coalfields in Germany by 2018, poses the risk of possible future mining damage related to mine water rise after mine closure. In this study, an interdisciplinary approach of structural geological and geochemical methods was applied to detect active fault zones, as a first step for long-term monitoring of mine flooding. The geomechanical analysis in the area of the soil gas campaign at the former coal mine “Haus Aden” shows high dilation and moderate slip tendencies as well as the potential for critical stress of the selected fault section of the Königsborn Fault. These features indicate the section under consideration as a preferred gas migration pathway. Soil gas measurements showed correspondingly clear anomalies of the components CO2, 222Rn and O2, which together with the results of the geomechanical analysis are a strong indicator for a structurally controlled migration of the gases and thus evidence of the modelled fault outcrop. A possible accompanying fault could not be identified properly, mainly because of the ambiguous CO2 concentrations. A positive correlation of CO2 and 222Rn can be a supplementary statistical tool to better assign unclear gas anomalies. However, this approach is limited by the radioactive decay of 222Rn and individual site parameters (groundwater, gas permeabilities). The primary mine gas CH4 could not be detected, which is probably related to its oxidative decomposition with formation of CO2. In the next step, it is planned to validate the current results with area-wide measurements if possible and then to expand selected boreholes to gas gauges. Newly developed, permanent gas sensors will be installed into these gas gauges for long-term monitoring of mine flooding. The aim is to provide new low-cost options for flooding monitoring in order to be able to estimate induced seismicity and mine damage. [ABSTRACT FROM AUTHOR]