Structure instability forecasting and analysis of giant rock pillars in steeply dipping thick coal seams

Structure stability analysis of rock masses is essential for forecasting catastrophic structure failure in coal seam mining. Steeply dipping thick coal seams (SDTCS) are common in the Urumqi coalfield, and some dynamical hazards such as roof collapse and min-ing-induced seismicity occur frequently in the coal mines. The cause of these events is mainly structure instability in giant rock pillars sand-wiched between SDTCS. Developing methods to predict these events is important for safe mining in such a complex environment. This study focuses on understanding the structural mechanics model of a giant rock pillar and presents a viewpoint of the stability of a trend sphenoid fractured beam (TSFB). Some stability index parameters such as failure surface dips were measured, and most dips were observed to be between 46° and 51°. We used a digital panoramic borehole monitoring system to measure the TSFB’s height (ΔH), which varied from 56.37 to 60.50 m. Next, FLAC3D was used to model the distribution and evolution of vertical displacement in the giant rock pillars;the re-sults confirmed the existence of a TSFB structure. Finally, we investigated the acoustic emission (AE) energy accumulation rate and ob-served that the rate commonly ranged from 20 to 40 kJ/min. The AE energy accumulation rate could be used to anticipate impeding seismic events related to structure failure. The results presented provide a useful approach for forecasting catastrophic events related to structure in-stability and for developing hazard prevention technology for mining in SDTCS.