Technische Hochschule Georg Agricola University
The German Coal Industry and its Knowledge of the Relationship Between Ground Water and Ground Movements
The German coal industry consists of two different branches that face different challenges in terms of ground water-induced ground movements. This is caused by previous underground hard coal mining and current open pit lignite mining. The production of hard coal stopped in 2018. In Germany’s hard coal regions, the Ruhr and Saar areas, ground water rebound is on its way. Lignite mining is still ongoing with a production rate of some 130 million tons (2022). Nearly half of the production is from the Rhenish region. The hard coal mining industry mined coalbeds within solid rock, overlaid by a sedimentary cap rock. Dewatering of the cap rock has caused measureable subsidence at the surface. The water rebound now causes an uplift. Lignite mining in the Rhenish region takes place in sedimentary formations that carry multiple ground water horizons. Open pit mining requires long-term dewatering around the mines. This causes ground movements at the surface. Once the pits are reclaimed, the ground water table is allowed to rise again, causing reverse ground movements. The correlation between ground movements and ground water is crucial especially near tectonic faults, creating a risk of damage of buildings and infrastructure. In a series of projects at the Post-Mining Research Center of Technische Hochschule Georg Agricola in Bochum (THGA), researchers observe and evaluate these ground movements and changes in ground water levels. From these studies, THGA is able to predict future subsidence and mitigation measures. Scientifically sound monitoring efforts are crucial for early warnings, risk-management, and communications with stakeholders. Researchers also use data from the European Ground Motion Service (EGMS) and the German Monitoring Service (Bodenbewegungsdienst, BBD). These platforms rely on satellites equipped with radar sensors, so that radar interferometry can be performed. Drones and terrestrial measurements are used for in-depth observations, for example during heavy rainfall.
Prof. Dr. Peter Goerke-Mallet studied mine surveying at the University of Clausthal-Zellerfeld in Germany. He worked for two years at the mining authority and then for almost 30 years at RAG, the largest hard coal mining company in Germany. At a deep anthracite coal mine, he was responsible for mine surveying, mine design and mine planning, mine subsidence engineering, environmental impact studies, public affairs and post- mining activities e.g. long term water management. For the past 10 years, he has been a lecturer at the Technische Hochschule Georg Agricola University in Bochum and a Senior Consultant for the Post-Mining Research Center.