Forschungszentrum Nachbergbau

Mine water, risk management, monitoring – when mining ends, it leaves behind a variety of tasks. How to deal with them responsibly was the focus of the 21st Altbergbaukolloquium from 9th to 10th November 2023 on the grounds of the UNESCO World Heritage Site Zeche Zollverein in Essen/Germany. Around 500 experts from all over Germany came together at the site, which is steeped in industrial history, to exchange ideas in the fields of geotechnics, mine surveying, mining, geology and civil engineering. The main focus was on the important question: What will the future look like after mining? This time, the symposium was hosted by the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany. “The colloquium on post-mining is one of the most important exchange formats for experts who deal with post-mining tasks and see them as an opportunity,” said Bärbel Bergerhoff-Wodopia, Member of the Board of the RAG-Stiftung, at the opening of the conference. “Scientific support for the technical processes of post-mining and well-trained specialists in this field are essential if the Ruhr region and mining areas around the world are to become regions worth living in.” “The steady decline in the extraction of fossil fuels is focussing on the phasing out of mining and the resulting tasks of the post-mining era,” added Heinrich Böckelühr, District President of the Arnsberg district government. “Examples include the planned increase in mine water in the state’s hard coal fields and the reutilisation of former mining areas for the further development of North Rhine-Westphalia as an industrial state. This also includes the expansion of geothermal energy and underground storage.” The Zollverein UNESCO World Heritage Site was therefore deliberately chosen as the venue for the conference. “It is an important landmark and identity creator for the entire region,” says Prof. Christian Melchers, Head of the FZN (Figure 1). “There are numerous opportunities here to explore the legacy of mining and develop innovative ideas for former mining regions. And for us as researchers, it is even an oversized real laboratory.” The FZN is currently carrying out several projects on the former colliery site. The colloquium’s varied programme of presentations also showed how application-oriented the current research topics are. The topics included the sustainable handling of mine water, increasing digitalisation in old and post-mining, the influence of climate change and specific remediation concepts for old shafts, spoil tips and entire industrial plants. (THGA/Si.)

Drone pilot Bodo Bernsdorf sees the world through different eyes. When he lets his special copter soar high above the grounds of the Zollverein coking plant in Essen/Germany, he not only encounters the chimneys and pipelines at flying height – he also finds damaged areas that are not even visible to the naked eye (Figure 1). The drone’s high-resolution images reveal how the industrial monument is really doing and where remediation is needed. That is at least the theoretical approach. Bernsdorf and his team from the Research Center of Post-Mining (FZN) at the TH Georg Agricola University (THGA), Bochum/Germany, want to detect material damage without leaving any traces themselves. In the new research cooperation “KoKo Zollverein” (short for “Copter flights on the Zollverein coking plant”), the FZN is developing and testing this new methodology. To this end, the experts are working closely with the Zollverein Foundation and the Materials Science Research Department of the German Mining Museum Bochum (DBM) in Bochum. Satellite images and non-destructive lasers will also be used in the troubleshooting process. Ultimately, the aim is to carry out a detailed examination of the building fabric and damage assessment for the first time.

For more than 30 years, coke, gas and other by-products were produced at the Zollverein coking plant in Essen. During peak operation, it was considered one of the most modern coking plants in Europe. Today, the plant is an architectural monument that, together with the neighboring Zollverein coal mine, has been declared a UNESCO World Heritage Site. “In addition to the cultural play and development of Zollverein, the preservation, safeguarding and protection of the UNESCO World Heritage Site is our top priority,” says Prof. Hans-Peter Noll, Chairman of the Board of the Zollverein Foundation. “Zollverein is a place of change and the future, so it is a perfect fit that a research cooperation is now testing cutting-edge technology in this huge real laboratory, which will soon open up new possibilities for other industrial-cultural sites.”

“The Zollverein World Heritage Site is a breath-taking landmark and an important witness to industrial innovation in our region” says Prof. Tobias Rudolph, project manager at FZN. “Every time we are on site with our scientific team, we get completely new perspectives. We are now expanding that with a sensor view from above and inside.” Indeed, it’s not just the outdoor facilities that are coming under the microscope; the interiors will also be evaluated. To do this, the drones take optical, thermal and multispectral resolution images that allow conclusions to be drawn about the condition of the materials. Where can rust be found? Where is verdigris or spalling? What is the overall condition of the objects? “At best, we can visualize all of this and then make a recommendation as to where the need for renovation is most urgent,” Bernsdorf explains.

For a holistic picture, FZN experts fuse drone data with satellite images from the European Copernicus program, which provide important information about the daytime surface. In addition, they combine the information from the air with on-site measurements in which a laser scanner scans the individual objects centimeter by centimeter. “For the first time, we are thus bringing together expertise from the fields of geomonitoring and materials science at a cultural and historical site. The idea of detecting material damage by interpreting and correlating various drone-mounted sensors together in a network is thereby a completely new approach in the field of historic preservation,” explains Prof. Rudolph enthusiastically. If successfully applied, the method will be transferred to other industrial heritage sites. (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.)

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.)

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.)