Longqing Shi

Coal-free zones, particularly scouring zones, reduce recoverable reserves and increase water inrush risk in coal mining. Existing sedimentological, geophysical, and geostatistical methods are often constrained by coring conditions, lithological interpretation accuracy, and geological complexity. Given that well log signals provide the most continuous carriers of geological information, this study integrates Singular Spectrum Analysis (SSA), Maximum Entropy Spectral Analysis (MESA), and Integrated Prediction Error Filter Analysis (INPEFA) to establish a multi-curve framework for analyzing the genesis and logging responses of coal-free zones. A two-stage SSA workflow was applied for noise reduction, and a Trend–Fluctuation Composite (TFC) curve was constructed to enhance depositional rhythm detection. The minimum singular value order (N), naturally derived from SSA-decomposed INPEFA curves, emerged as a quantitative indicator of mine water inrush risk. The results indicate that coal-free zones resulted from inhibited peat-swamp development followed by fluvial scouring and are characterized by dense inflection points and frequent cyclic fluctuations in TFC curves, together with the absence of low anomalies in natural gamma-ray logs. By integrating multi-curve logs, core data, and in-mine three-dimensional direct-current resistivity surveys, the genetic mechanisms and boundaries of coal-free zones were effectively delineated. The proposed framework enhances logging-based stratigraphic interpretation and provides practical support for working face layout and mine water hazard prevention.

Accurate prediction of the water-bearing capacity of aquifers is crucial for protecting the surface ecological environment and ensuring safety during coal mining. In this study, a macro–micro combination was used to investigate the water-bearing capacity of bedrock aquifers. At the micro-level, the micro pore parameters of various sandstones were determined through cast sheeting. At the macro-level, the porosity and water absorption rate of various sandstones were determined experimentally. After that, a new index weighting method was proposed to comprehensively evaluate the water-bearing capacity index of sandstone. According to this method, the water-bearing capacity of aquifers in the Guojiahe coalmine were evaluated. The research results revealed that the water-bearing capacity of sandstone was mainly related to its pore connectivity, and the water-bearing capacity of sandstone in the Luo’he and Zhi’luo formation was considerably greater than that in the Yan’an formation. The water bearing capacity of strata in the eastern part of the mining area is lower than that in the western part of the mining area. The research results can provide considerable money savings for coal mining and protect the ecological environment and groundwater resources in the region.