A case study of spatial and temporal microseismic evolution and surface subsidence during room and pillar trial tests

Deep ‘room and pillar’ (R&P) mining without subsequent depillaring offers a low-impact alternative for extracting coal beneath sensitive surface infrastructure, yet the geomechanical behaviour of such operations at depths approaching 900 m remains poorly understood because seismicity and subsidence research have evolved largely independently. Key scientific and engineering contributions are represented by coupled analysis of induced microseismicity and surface deformation during a deep R&P trial in the Czech part of the Upper Silesian Coal Basin, where high-grade coal was extracted from a shaft protection pillar at depths of 700 to 900 m. A dual-scale monitoring architecture, combining regional seismological networks with local seismoacoustic sensors and precise surface levelling over six years, captured the mechanical response with metre-scale spatial resolution and millimetre-scale vertical accuracy. The study identifies two distinct anomalous seismic regimes: stress redistribution during roadway approaches to existing workings, which intensifies at face-to-roadway distances of 13 to 16 m, and wide-area activation of reverse tectonic faults triggered by incremental excavation. Pillar compression emerged as the dominant deformation mechanism, generating low-energy seismic events and limiting maximum surface subsidence to 17 mm, a value validated through Knothe influence function calculations driven by measured roof convergence. These results establish the first empirical seismicity-subsidence dataset for non-retreat deep R&P mining, provide a replicable monitoring protocol for similar depth regimes, and demonstrate that this extraction geometry can substantially mitigate surface impact relative to longwall alternatives.