THGA

Resources are becoming scarcer, energy prices are rising. In addition, dependence on third countries has led to a global rethink when it comes to extracting raw materials. New ways must be found to extract valuable materials ecologically and economically. That these ways also follow unusual ideas is shown by a new project that has now started at the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany: Over the next two years, the scientists in the “IAW3³” project will investigate whether strategic raw materials can still be extracted from mine water and which methods are best suited for this. With the help of new processing technologies, critical metals in particular are to be extracted. The experts not only look at the mine water itself, but also examine its precipitation products and treatment residues. They conduct their investigations at various mines in the Ruhr, Saar and Ibbenbüren regions.

The research project is initially funded by the RAG-Stiftung, Essen/Germany, until 2024. The full project title is: Innovative processing technologies and their potential for recovering valuable materials from mine water, precipitation products and processing residues at Ruhr, Saar and Ibbenbüren with special consideration of critical metal resources, in short: IAW3³.

“For us, post-mining does not only mean dealing with the challenges that the coal industry has left us. In the field of post-mining, it is also a matter of developing new possibilities and opportunities in the former coalfields,” says Bärbel Bergerhoff-Wodopia, Member of the Board of Executives of the RAG-Stiftung. “The new research project around the extraction of strategic raw materials from mine water is a highly exciting field of the future that is geared towards sustainability. It can contribute to reducing dependencies in raw material extraction. Just how important independence can be in this field is particularly evident to us these days. That is why we as the RAG-Stiftung are very happy to support this special project.”

“We see mine water as a potential stream of valuable materials,” says Prof. Christian Melchers, who heads the project at FZN. “The innovative thing about our idea is that we not only look at the mine water itself, but also examine the residues from treatment and its precipitation products. Precipitation refers to the separation of a dissolved substance from a solution.” What is sludge and silt for the layman is a real treasure trove for the experts at the FZN: “Recent investigations have shown that it contains, e. g., magnesium, which is used in engine construction. In the past, there have already been supply bottlenecks with the Chinese market leader. At best, we want to counteract these dependencies,” explains project member Bastian Reker (Figure 1). Rare earths, which can drive the expansion of renewable energies, or lithium, which is crucial for e-mobility, are also found.

The scientists are also examining the quantities of the critical element germanium in the mine water. “This is a by-product that is otherwise only produced during zinc extraction and is essential for the coating of fibre optic cables and thus for the expansion of the network,” says Reker. “Currently, all of these raw materials are being extracted worldwide under sometimes dubious environmental standards that affect people and the environment equally,” adds Prof. Melchers. “This simply no longer fits in with the spirit of the times and the growing ecological awareness in our society. We therefore want to initiate a rethink, accompany the processes scientifically and thus look for new possibilities on our own doorstep.”

The mine waters that are lifted from great depths with pumps in the former coalfields of the Ruhr, Saar and Ibbenbüren show a wide range of different mineralisations and enrichments – depending on the regional geology, hydrogeology and other influencing factors left behind by mining, explains expert Prof. Melchers: “We are now examining the extent to which it is also economically worthwhile to collect and process these valuable substances.”

To this end, the scientists will be setting up their own precipitation reactors at suitable locations in the coming months. In them, iron and other metals will be separated in a targeted manner by adding oxygen. They want to transfer the knowledge they gain from designing the plants on a laboratory scale to experimental plants on a large scale. In the IAW3³ project, the scientific team is also testing completely new processing technologies. Hyperspectral sensors, e. g., could help to directly detect the critical metals in mine water and co. and assess their mineralogical composition in a matter of seconds. The most promising methods are to be further developed at the FZN. (THGA/Si.)

Coldewey, W. G. (2022): Handbuch Hydrogeologie. Das Standardwerk für Lehre und Praxis. First edition. 713 pages, 104 tables, 178 figures and 42 appendices. Vulkan Verlag GmbH Essen (Figure 1).

The importance of water as a geo-resource for the people and the environment has been emphatically brought to the attention of the public in recent years. The orderly handling of water must be the focus of all professionals who are responsible for processes that influence the natural water cycle. This involves the extraction, use, purification and discharge of water, but also the protection of the public from the power of water, its retention and availability. Hydrogeology provides the basis for an understanding of the processes surrounding the geo-resource water.

The Handbook of Hydrogeology lives up to this requirement and undoubtedly offers benefit for all hydro geologically interested professionals in the sense of a standard work for teaching and practice. Thus, already when opening the book, which is widely illustrated with figures, tables and appendices, the competence of the author, who has been known for decades in wide circles as a proven expert in hydrogeology, becomes clear. Indeed, one very quickly feels literally “at home” in the topic and hardly wants to put it down.

The book is divided into the major chapters “General Hydrogeology”, “Applied Hydrogeology” and “Groundwater Characteristics”. From a scientific-technical point of view, the physical-chemical basics covered in this work are very welcome. This includes the numerous definitions of terms used throughout from standards, guidelines and guidance documents. Formula symbols are abbreviated with the letters that are also used internationally, equations are documented by figures that explain the corresponding formula designations and substantiate them with example calculations.

The present work is characterized by an extensive bibliography and a comprehensive compilation of relevant DIN standards. Literature has been compiled according to the usual citation specifications in geology, allows a good overview of the scope and facilitates the finding, even of unusual titles. The appendix contains various thematic maps from the fields of geology, hydrogeology and water management, which are very clearly illustrated in color in the form of a model landscape.

The book facilitates the user’s entry into and in-depth study of all aspects of hydrogeology through its very thoughtful and descriptive layout in terms of graphics and topics. The quality standard of the author, who has a profound experience in the field of hydrogeology, both in practice and in teaching, is evident. Both experienced professionals and young people will certainly be attracted to the work in their interest in hydrogeology. From the point of view of the depth of content, the scope and the elaborate design of the book, the price of 149 € is reasonable.

In the sense of creating transparency and understanding for the manifold questions that arise in view of the complexity of the georesource water, this standard work can be recommended for reading and use by all experts and students dealing with the subject, but also by all other interested parties.

Prof. Dr.-Ing. Peter Goerke-Mallet, Research Center of Post-Mining (FZN), TH Georg Agricola University (THGA), Bochum/Germany

Mining leaves its mark – water in particular as a resource in the former mining regions is affected by the consequences of intensive raw material extraction, some of which has been ongoing for centuries. The key issues in this year’s “NACHBergbauzeit in NRW” conference (Figure 1) looked at the challenges involving the long-term management of water and the resulting effects from the planned increase in pit water levels. The District Government of Arnsberg as the mining authority for North Rhine-Westphalia and the TH Georg Agricola University (THGA), Bochum/Germany, held the joint specialist conference for the sixth time on 10th March 2022. The 250 or so participants exchanged their professional views online on the subject of “Pit water – planned on paper, discussed online”.

In his welcoming address, Hans-Josef Vogel, District President of the District Government of Arnsberg, emphasised the vital cooperation of universities and public administration: “This innovation partnership guarantees the scientific basis for problem solving in the economy, in communities and in civil society. The research into post-mining is a very tangible example of how we can open up new vistas together, with a view to climate protection.”

Bärbel Bergerhoff-Wodopia, Member of the Board of Executives of the RAG-Stiftung, Essen/Germany, added: “In times of a recycling economy, but also with the increased use of georesources, among other things, for electric mobility, it is important to think about post-mining. For only with our post-mining experience can we succeed in using georesources sustainably today and in the future – this will only be the case if post-mining is considered right from the start in every mining process.” New ideas and innovations are needed to resolve the challenges of the future together and to unlock brand new potential.

The presentations of the conference primarily addressed the effects of the planned increase in pit water on the mining districts in North Rhine-Westphalia and in the Saarland. The speaker, Thomas Im-grund from DMT GmbH & Co. KG, explained the possible effects of rising water levels on pit gas extraction. He also estimated the overall possible impacts of the process on the emission of methane on the ground surface. He concluded with a positive outcome. With targeted extraction and utilisation of the pit gas, uncontrolled emissions would decrease considerably. The rising pit water would also cause flooding of flow paths and a lower gas output overall in the long term.

Manuela Nie and Mario Sommerhäuser from the Emschergenossenschaft/Lippeverband (EGLV), Essen/Germany, offered a very different view on the pit water. In their pre-sentation, they addressed the significance it currently has and will have on the flora, fauna and water quality in the Emscher-Lippe region. Overall, they acknowledged that the region demonstrated good ecological development. The impacts of pit water discharge are currently very low due to fast and heavy dilution in the river waters, which is perhaps why the salt concentration is well below the limit – and they continue to decrease. According to the EGLV’s plans, the whole Emscher will be completely free of pit water from September 2022.

The presentations in the second part of the event covered the challenges faced regarding the responsible handling of PCBs. This abbreviation stands for polychlorinated biphenyls; chemical chlorine compounds which were used in the coal mining industry, e. g., in hydraulic systems, transformers and gearboxes. The fact that PCBs are potentially harmful to human health and the environment was not known for some time. The use of this substance was not forbidden until the mid 1980s – traces can still be detected in pit water today, albeit in very low levels.

In his speech, Michael Denneborg presented a report commissioned by the North Rhine-Westphalian regional government to assess possible risks for ground waters and surface waters. In it, the qualified geologist from ahu GmbH, Aachen/Germany, looked at the possible effects of rising pit water on the discharge of PCB and other residual materials. His conclusion: Overall, higher pit water levels reduced the flow of PCB and the pit water volume in bodies of water over the long term.

Following this, Joachim Löchte from RAG Aktiengesellschaft, Essen/Germany, presented the intensive monitoring programmes developed by the company in order to constantly check and systematically record the flow of PCB into pit water. He covered the technical challenges faced during monitoring in particular. He also presented current projects the RAG is working on, with scientific support from the Research Center for Post-Mining (FZN) at the THGA, with the aim of further minimising contaminants, e. g., using special filters and treatment plants.
(Carmen Tomlik (THGA)/Si.)

At the Research Center of Post-Mining (FZN) at TH Georg Agricola University (THGA), Bochum/Germany, Julia Tiganj (Figure 1) is studying the socio-economic aspects of post-mining. In times of raw material scarcity and the energy transition, the economics researcher’s attention is especially drawn to China. Will the world’s second-largest economy manage the transition to renewable energy? What are the greatest challenges they face and what will the rest of the world gain? There’s not much research yet but the topic is super hot right now, says Julia Tiganj being interviewed by Carmen Tomlik from the FZN.

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Carmen Tomlik: In your expert opinion, where does China stand on the energy transition and on post-mining?

Julia Tiganj: That depends on where you look. There are many provinces in China which vary greatly, e. g. in their reliance on coal. There are regions which are already working sustainably. On the other hand, there are provinces whose economies rely heavily on mining. Here, coal secures a lot of jobs, taxes, pensions and, of course, supports national economic growth – which is one of China’s primary goals. As you can see, the gulf between them is massive. For this reason, it will be difficult in future to meet the many different economic requirements and the needs of the people in the different regions. There are interesting pilot projects, e. g., some people are thinking of using old, disused mines to create “underground cities” to compensate for the demand for space in the cities. Of course, the idea is controversial – but it is quite an innovative one and begins to face the issues of post-mining. China is also a global leader in satellite technology. Here the question is how far this expertise is being used to monitor the legacy left by mining.

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Tomlik: China without CO₂? What are the greatest challenges on the way to carbon neutrality?

Tiganj: Coal is still the easiest and safest way to secure a stable energy supply. China intends to become carbon neutral by 2060. However, this also means that the highest CO₂ emissions peak needs to be behind them by 2030. At the moment, they are therefore still building new coal power plants which are designed to run for 40 years. These power stations, however, meet the latest environmental standards and are intended to replace out-dated, inefficient plants. At the same time, China is already a market leader in renewable energy. Around 90 % of the energy concentrates used in solar panels, silicon batteries or wind power are made here. Until now, preventing climate change had no priority within China itself. The latest five-year-plan, however, demonstrates that China wants to become “greener” and has recognised the urgency of this.

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Tomlik: What does “greener” mean in this case?

Tiganj: That’s the next big challenge. After all, renewable alternatives also produce CO₂ and are not yet 100 % recyclable. The rotary blades of wind turbines, e. g., are disposed of as hazardous waste after being in use for only 20 years. Air pollution or poisonous wastewater threatens certain areas of land and the people who live there so that clean energy can be produced in a different part of the world. This is not sustainability, this is a displacement of climate problems from A to B under the smokescreen of a green future. As you can see, the whole setting is far from ideal – and now we haven’t even talked about the labour market and the long-term challenges that structural change would bring to Chinese coal-mining areas. Nevertheless, it is an important step to say: We are reorienting ourselves, we are doing research and we want this transformation.

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Tomlik: What would the rest of the world gain if China becomes carbon neutral?

Tiganj: When large, influential players like China pay more attention to sustainability and protecting the climate, this has a positive impact on everyone else. Direct neighbour states often orient themselves in accordance with dominant China and its approach. Depending on import and export dependencies, other countries may also find it necessary to reorient themselves in order to keep up. Also, China is an important trade partner in rare earths and is highly influential on the advances of e-mobility in Europe or the USA. This and many other aspects are factors which are helping processes to become more sustainable globally. Generally, a lot of research and development is still needed in order for the energy transition to be successful. Here too, a “green” China could become an international driver of innovation. (THGA/Si.)

The Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, has a broad field of focus. When it was established in October 2015, research focused initially on the perpetual tasks of the German coal mining industry: long-term mine water management, the management of polder areas and groundwater purification on former mine sites. In May 2019, the FZN added “geomonitoring in post-mining” to its research profile. The aim of this research is to develop innovative technical systems for the integrated monitoring of post-mining activities. The FZN celebrated its fifth anniversary in 2020 and since then has expanded its research further to include “materials science for the preservation of industrial heritage” and “reactivation and transition”.

As a result, the FZN has all the skills and expertise required to help make the post-mining era sustainable, environmentally friendly and economically successful. The aim is not only to preserve this ever-growing expertise, but also to apply it in new ways. The interdisciplinary team shares its findings at specialist conferences and in working groups, and also makes the information available to the public in the form of studies and publications. Since 2019, the FZN’s final reports and studies have also been available as part of its scientific series “Reports on Post-Mining,” which is self-published by the THGA. Two reports have been published to date. In these reports, the authors examine aspects of the mine water rebound process in underground mines.

Volume 1 “Evaluation of Mine Water Rebound Processes” (Melchers et al., 2019) compiles the diverse experiences gained in the long-term and environmentally friendly management of mine water in selected European coal-mining districts (Figure 1). The hydrogeological, mining and water management aspects are systematically evaluated and site-specific features identified. The findings help to illustrate the mine water rebound process and aid understanding. Building on this, volume 2 “Model-Based Sensitivity Analysis of System-Determining Factors”(Westermann, 2000) provides an overview of the key natural and anthropogenic influencing factors. The scale of the effects of certain factors is determined for three underground mines by way of an example and applied to other sites. The findings are used to help actively shape the mining life cycle and plan ahead for the post-mining era.

The plan is to continually expand the scientific series “Reports on Post-Mining” with the FZN’s wide-ranging findings on the topics of mine water management, geomonitoring, materials science and structural change measures. Previous and future reports can be accessed free of charge in digital format at www.nachbergbau.org/berichte-zum-nachbergbau. (THGA/Si.)

Our underground is on the move. However, the shocks are often so small and spatially restricted that they are only detectable for very sensitive sensors. Even where mining was once conducted and people interfered with the natural geology and deposits, it may subsequently cause microseismic shocks. Paloma Primo, scientist at the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, pursues these mini-movements. In the new research project “PostMinQuake”, the expert examines how they occur exactly, identifies particularly endangered structures and develops a long-term risk management system for affected regions (Figure 1). To this end, she works closely with many European partners. Because also in the Czech Republic, Poland and France the post-mining period should not become a “nail-biting affair”. “The joint project is just as complex as the circumstances underground”, says Primo. “Our investigations go beyond the simple connections between seismicity and the geological activities in the decommissioned coal mines partly filled with water.”

Experts from various disciplines are working together in the project, including surveyors, geotechnical engineers or hydro-logists. Together they monitor the geological dynamics in the respective test areas, which have been changed by coal mining – in Germany this is mainly the Ruhr area, the Ibbenbüren and Aachen mining districts. “In these areas we document microseismic activities underground roughly once a week. There are also records from the past, which we analyse and put into context.” Primo obtains her data from the Geological Survey NRW, RAG Aktiengesellschaft, the Institute for Geosciences and Natural Resources (BGR), as well as seismological stations at the Ruhr-University Bochum (RUB). “At these stations we can determine time, size, place and depth of the event.”

The experts are pursuing an important common objective, explains Primo: “With our research we want to guarantee long-term safety, create transparency and inform the public. Because every municipality and every former mine operator should have sound knowledge of the processes that take place underground. When it comes to the topic of ground movements there are many fears and misunderstandings about what microseismic events are and the effects they can have.” Therefore, the main objective of the project is to gain a better understanding of the mechanisms of microseismic events after mining and create plans for the long-term monitoring of the soil after mining.

What external factors cause the micro-shocks? What factors can be used to realistically simulate the impacts on the PC? And how can satellite images help to properly interpret the data acquired from underground? “We’re talking here about vast amounts of data, which first of all we have to standardise in order to make it comparable and then be able to evaluate it using the latest methods”, says Primo. Over the next three years the project team will develop a reference database from the findings for European areas after mining. The research should also help to develop new monitoring strategies and interpretation methods for areas with increased risk of earthquakes. The project is part of the EU-financed Research Fund for Coal and Steel (RFCS). (THGA/Si.)

Construction sites, closures, narrowed lanes: Since the end of March 2020 the patience of drivers who use the Dortmund/Witten motorway junction is being tested. But the remediation work on the A44 is urgently required, says Cedric Kamgaing Kamdom: “ Most recently we detected and backfilled a hollow space, which was around 10 m high and 3 m wide – roughly as big as a single-family house. And it was just below the road surface”, explains Kamgaing Kamdom, who works as a project manager at the responsible engineering firm arccon -Ingenieurgesellschaft mbH, Gelsenkirchen/Germany. The experts have now piped around 800 t of concrete mix into the holey underground in order to secure it. This corresponds to around 30 full semitrailers.

The near-surface cavities originate from olden times: At one time the miners here mined the -Vereinigte Wiendahls-bank mine through the ground. The mine closed down in 1924. The available data is sparse.

“The plans for the deposits are over 100 years old. This does not make it any easier for us.” Apart from that, there is also the so-called illegal mining, which is not recorded anywhere. You cannot simply drill straight over it, explains Kamgaing Kamdom: “Our most important task is to optimally detect the suspected cavities in order to save time and costs.”

And the concrete mix needs to be carefully chosen, depending on the nature of the cavities and loose zones. At the beginning of such a project is a basic evaluation, during which old mine plans are also evaluated. They can provide guidance on surface openings, old tunnels or working areas of a mine. Following this basic research, if necessary exploration, safety and safeguarding works are planned, tendered and executed in the form of drilling and backfilling at extreme depths.

Specialist knowledge that Kamgaing Kamdom acquired in the course of his studies. Five years ago he came from Cameroon to Germany and decided to study at the TH Georg Agricola University (THGA) in Bochum. He acquired a fresh perspective in the master programme “Geological Engineering and Post-Mining”: “I was unfamiliar with the labour market beforehand, but did know that the coal mining sector in Germany was due to end in 2018 and that then certainly people who are knowledgeable in post-mining would be recruited”, says Kamgaing Kamdom, who already studied geosciences in his home country.

He turned out to be right. Experts at the interface between mining, surveying and geotechnical engineering are not only in demand here in Germany, but also internationally. Because the mining of raw materials leaves its mark worldwide (Figure 1). Special safety and restructuring measures are required in order to manage the risks at former mining sites. The master programme at the THGA, which is the only such programme offered in Germany, trains engineers to responsibly plan and execute the complex processes of mine closures and the aftercare. This also includes intelligent after-use in the affected regions.

For Kamgaing Kamdom the language was initially a little obstacle. “Especially in the lectures I had to be very attentive, but the good contact with other students and the lecturers made things a lot easier. The course is also very practical and you are out and about on the road a great deal”, says the graduate.

And what’s happening now on the A44? “We are currently on schedule. But there is still one part to come.” Here there may be more unexpected challenges hiding somewhere for the engineers, but Kamgaing Kamdom is confident: “When we have completed our work, probably in summer 2021, we are forever on the safe side.” Ideally, for drivers this means: For starters, peace and quiet on the A44. And for Kamgaing Kamdom: Off to the next construction site! Because the post-mining era is significantly longer than the mining era itself and brings full order books also in the future. (THGA/Si.)

Save the date: Bereits zum sechsten Mal veranstalten die Technische Hochschule Georg Agricola (THGA) und die Bezirksregierung Arnsberg ihre gemeinsame Fachtagung. Thema diesmal: „Grubenwasser – analog gedacht, digital diskutiert!“ Dazu treffen sich die Expertinnen und Experten dieses Mal ausschließlich online!

Wie gelingt ein verantwortungsvoller Umgang mit den Folgen des Bergbaus? Und welche Perspektiven bietet die Nachbergbau-Ära für Mensch und Umwelt? Diese Fragen stehen im Mittelpunkt der kommenden Fachveranstaltung NACHBergbauzeit in NRW. Die THGA und die Bezirksregierung Arnsberg als Bergbehörde NRW führen die interessierte Öffentlichkeit sowie Expertinnen und Experten der Branche zum intensiven Themenaustausch zusammen. Der Dialog im März 2021 findet erstmals als Online-Konferenz in der Zeit von 10:00-13:00 Uhr statt. Sie sind hiermit herzlich eingeladen, sich an der digitalen Diskussion zu beteiligen.

Themen 2021:

• Welche technischen Herausforderungen ergeben sich beim geplanten Grubenwasseranstieg in den ehemaligen Steinkohlerevieren an der Ruhr, der Saar und in Ibbenbüren?
• Grubenwasseranstieg europaweit: Was können wir von unseren Nachbarn lernen?
• Welche Methoden eignen sich zur langfristigen Überwachung von Bergbaufolgen?
• Wie lassen sich die Erkenntnisse aus der Steinkohle auch auf andere Bergbauzweige übertragen?

The history of mining is long – but the history of post-mining will be much longer. For five years now the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA) in Bochum/Germany has been attending to the issues that emerge as mining activity ceases. As the world’s first institution, it takes a comprehensive look at the post-mining era. The scientists are examining not only the tasks that mine water or former mining areas leave behind. They are also developing modern monitoring methods, advising affected regions on the structural transformation and trying to preserve the industry culture.

“The challenges of post-mining are complex, that’s why we are also becoming increasingly complex”, says Prof. Ulrich Paschedag, Head of FZN (Figure 1). “Since October 2015 we have been pooling the necessary know-how to shape the consequences of mining in a technically, economically and environmentally friendly manner.” In the interdisciplinary team around 40 independent experts in mining, geology and geo-technology, hydrogeology, chemistry, electrical engineering, materials science, land development, mine surveying and economics, all work closely together. This is the core around which a broad network has been established, nationally and internationally.

In the beginning the focus was still on researching the so-called perpetual tasks of the coal mining industry, but the FZN has been expanding its focus to this day. From the integrative approach come the four research areas: perpetual tasks and mine water management, geomonitoring in post-mining, materials science for the preservation of the industrial heritage, as well as reactivation and transition.

The experts are currently developing the scientific bases for an ecologically and economically compatible mine water ascent. The experiences from other European territories, in which such processes have already taken place wholly or partly also help. “The mine water rise is technically controllable”, says Prof. Christian Melchers. “Now it is about designing sustainable water management systems within the closed mines. Only then can the water resources in the former mining landscapes be reshaped in a near-natural way”, states the expert. The findings can also be transferred to other mining activities such as lignite or the gas and oil industry.

In the future geomonitoring will be about monitoring the impacts of mining over the long term using modern technology. “For this we must skilfully connect lots of information – like with a puzzle”, states Prof. Tobias Rudolph describing his area of research. Satellite data, historical maps, soil samples or multispectral aerial views with the drone are used here. “From these we can draw conclusions, e. g., about soil changes and detect changes in the vegetation.” In close cooperation with materiaIs scientists at the German Mining Museum (DBM) in Bochum, new methods are also being developed at the THGA to slow down or ideally stop ageing processes. The post-mining experts are helping to preserve the industry culture such as old winding towers or blast furnaces.

The cutting-edge research in the area of post-mining is in demand worldwide. More and more countries are interested in a far-sighted approach for handling active and former mining sites. The knowledge from Bochum also helps to make future mining processes more environmentally friendly. The FZN is in constant dialogue with its many international partners. It will also remain challenging in the future. “We are concerned with highly complex questions and interrelationships that take place in locations that are frequently still difficult to access. Underground, e. g., in places most people have never been to, and which will soon become inaccessible to all of us”, says Prof. Paschedag. “This is the reason why we, as scientists, have to make a special effort to formulate our post-mining findings in a way that can be generally understood by everyone.”
(THGA/Si.)

RAG Aktiengesellschaft, Essen/Germany, started to digitise abandoned surface openings, shafts and mining galleries of the coal mining sector via the Sigfox-0G network. There are around 60,000 in North Rhine-Westphalia alone. The aim of this IoT connection is the continuous monitoring of changes in real time in order to increase protection against sinkholes and reduce the effort of on-site inspections. The Sigfox–0G-based mining shaft monitoring system, which is also used for long-term documentation, has been designed by the Research Center of Post-Mining (FZN) and the Electrical Engineering/Information Technology and Industrial Engineering research sector of the TH Georg Agricola University (THGA) in Bochum/Germany and developed to series production in cooperation with the RAG (Figure 1).

The 0G-based remote monitoring system which is operated by a solar generator comprises pull-wire switches and a microcontroller with radio transceiver, which transfers the data via Sigfox-0G networks to a monitoring cloud. The sensors monitor, e. g., the vertical movement of the filling column of an old mine shaft. The data collected via Sigfox-0G network can be shown in the cloud for monitoring purposes and in the event of an alarm can be automatically sent to a predefined message chain by SMS and e-mail.

“It is necessary to constantly monitor the over 5,200 km² hard coal easements in our area of responsibility which have around 7,200 former surface openings because sinkholes are possible at any time in a section of around 100 km². Therefore, around 6,000 inspections are carried out every year in order to be able to take preventative action in good time. To minimise these on-site inspections and for real-time monitoring of any changes, selected surface openings are now also constantly monitored via a Sigfox-0G network connection”, says Frank Wollnik from the Site and Geo Services Division of RAG.

“The Sigfox-0G solution for shaft monitoring is an element of the so-called Mineberry system, which works completely independently and is solar-operated and is suitable for almost every type of old mining objects thanks to the modular structure. In order to implement the cloud connection of our remote monitoring solution in a manner that is cost-efficient, long-lasting and maintenance-free, we connected proven sensor technology to the innovative Sigfox-0G network. And as it can be used worldwide without any roaming charges, our solution can also be used worldwide”, explains Prof. Bernd vom Berg, Head of the Laboratory for Electrical Measurement and the Laboratory for Microprocessor Technology at the THGA.

“The RAG monitoring system is an excellent example of the remote monitoring of things and states, which up to now could not always be given special attention because it was too expensive or too energy-hungry to record all this data in real time. However, with Sigfox 0G real-time monitoring of even the simplest objects and states is possible. In the case of mining, it is easy to imagine that there are many control points worldwide, which can be monitored via a Sigfox-0G network. Especially because after the fossil-fuel phase-out no more money is earned, cost-efficient and low-maintenance data communication channels like Sigfox-0G offers are particularly important”, explains Stéphane Pâris, Technical and Network Director at Sigfox Germany.

The 0G controller is installed aboveground outside the possible Ex zone for the remote monitoring system for surface opening monitoring, whereas the Ex-protected sensors are installed in the shaft. As radio signals can be transmitted via the Sigfox-0G network across many kilometres, their use is also possible in areas with a poor mobile phone connection. The controllers can also be operated for many years without changing the batteries thanks to the battery-saving radio technology. Installations in the equally radio-critical underground environment can be found in the water supply network of the city of Antwerp. However, prerequisites for extensive underground installations are repeaters, which must be positioned every 3 to 5 km. (THGA/Si.)