Water Inrush Evaluation, Prevention and Control Technology for Coal Seam Floors Threatened by Highly Pressurized Ordovician Limestone Water

To mitigate high-pressure Ordovician limestone water inrush hazards at the 3203 working face of Hongshan Coal Mine, a synergistic water inrush mechanism is proposed involving mining-induced stress and concealed structures. Based on field measurements and theoretical analyses, this study established a mechanical model of floor failure and derived the critical conditions for water inrush. The vulnerability index method was employed to develop a risk assessment model incorporating five multisource indicators, with combined weights determined using the analytic hierarchy process (AHP) and the entropy-weight method. A whole-process prevention and control system covering the pre-mining, mining, and post-mining stages is also proposed. The results show that mining-induced fractures and concealed structures progressively propagate under cyclic mining-induced stress. Delayed water inrush is triggered when the cumulative propagation amount, ΔH, exceeds the thickness of the aquiclude. The vulnerability index method divides the study area into seven risk levels. TS1–TS4 (water bursting point 1–4) were used for model development, and TS5–TS6 were reserved for independent validation. The identification rates were 100% on both the modeling and independent validation datasets. Leave-one-out cross-validation yielded a mean identification rate of 83.3% with a standard deviation of 0.14, outperforming the conventional water inrush coefficient method. After implementation of the whole-process prevention and control system, water inflow at the working face stabilized at 0.4–0.6 m3/min, representing a 60–73% reduction compared with the untreated working face, which was shown to be statistically significant (p < 0.01) using the Mann–Whitney U test. The critical conditions established in this study provide a semi-quantitative mechanical basis for identifying floor water inrush. The proposed prevention and control system has considerable potential for application in coal seam extraction under similar geological and hydrogeological conditions.