In this interdisciplinary project, in cooperation with industrial partners as well as geodesists, geomechanics, geophysicists and geologists, possible threats to selected German hard coal mining areas caused by mine water rise are being investigated. The focus is on heterogeneous ground uplift, stress changes due to the change in pore pressure caused by mine water rise and the reactivation potential of disturbances. The hard coal mining areas are among the best documented areas worldwide. The successive end of hard coal mining in the different coal mining areas in Germany until 2018 shows different stages of mine water rise with accompanying heterogeneous soil uplift and induced seismicity. The cause is an increased pore pressure in the poroelastic rock body, which meets a mining-related stress distribution. Furthermore, the flooding leads to a changing strength of fault lines and mass differences in reservoir compartments, which can lead to induced seismicity. Thus, all relevant physico-chemical parameters that lead to hazards as well as the temporal development due to the different end of coal mining can be used in a large-scale experiment. Because the separation of induced and tectonic seismicity in seismically active areas is difficult (Slo 2016), the project will consider the Saar and Ruhr areas, both of which are described as tectonically passive areas. Changes in mine drainage have been taking place in the Saar area since 2013, while in the Ruhr area initial measures are planned for 2019. In 2015 fluid-induced seismicity with magnitudes up to 2.7 was measured in the Saar area.

The aim is to gain a deeper understanding of the process through the geomechanical coupling of geodetic surface deformations with stress changes in the subsurface due to the rise in mine water, in order to be able to estimate mine damage and induced seismicity in critical areas. The determination of potentially isolated compartments in the subsurface should lead to estimates of whether different uplift rates and a derivable reduction of the perpetual loads are possible for future flooding concepts. Using low-cost sensors to measure the physical quantities and the novel coupling with the simultaneous measurement of gas leaks, low-cost methods for the detection of seismic events are tested, which can then serve as an early warning system. This is supported by automatic detection and localization algorithms.

The results can be transferred to action plans for future flooding measures in mining. The research approach of coupling different compartments separated by structures with the observed influences on soil uplift and associated microseismicity is novel and allows an evaluation of differently controlled groundwater rises for the individual compartments to reduce the potential risk of induced seismicity.