Evaluation of an Old Coal Mine in the area of GeothermieZentrum Bochum by Geophysical Prospection - Field Measurments in Search of Empty Spaces or Weathered Material in the Subsurface

Master's Thesis from the year 2016 in the subject Geography / Earth Science - Physical Geography, Geomorphology, Environmental Studies, grade: 2.0, Ruhr-University of Bochum (Geology and Minerallogy), course: Geophysical Prospection, language: English, abstract: This study, aims to establish an evaluation workflow using geophysical measurements to prevent building hazards due to ground collapse, settling and subsidence in areas with former mining activity. This workflow should be applicable to locations with a similar historical background to the study site to attain public safety, providing an alternative, urban friendly and non-destructive inspection method. Geophysical measurements are often used to determine the state of the underground and to detect possible structural weaknesses. In contrast to the direct underground investigations, like drilling, the on-surface prospection is less expensive and less destructive. This study is intended to investigate the applicability of geophysical measurements for the determination of the subsurface stability of an old coal mine in the area of GeothermieZentrum of Bochum. Former studies and reports of the selected area were taken into consideration to approximate the geological and structural condition of the subsurface. These reports incorporate information about the preceding restoration projects that took place along the last 40 years and help us gain a sufficient image about what is to be expected into the subsurface. This information was used in combination with the geophysical data, obtained during the current study, to attain results about the state of the ground and to create general implications for the suitability of geophysical investigations of old near-surface coal mines. The used geophysical methods are the ground penetrating radar (GPR), geoelectric prospection, and seismic refraction. The collected data were processed and evaluated with several specialized programs, such as, ReflexW, Geotom, Bert, Res2DInv, and FMtomo. The maximum estimated penetration depth through the final inversion process is 30-40 m, depending on the type of the survey.