Background As coal mining in mines constantly expands to greater depths, water hazards in the Ordovician limestone aquifers of coal seam floors pose a serious threat to the mining of coal seams in lower formations. Fault reactivation represents a primary factor inducing water inrushes. However, the original water inrush coefficient (T = p/M) suffers from certain limitations when used to assess the water inrushes in areas with faults.

Methods Four models of floor water inrushes induced by non-penetrating faults (i.e., concealed hydraulically conductive faults, concealed isolated faults, and exposed faults) and penetrating faults were constructed, and the mechanisms behind various water inrushes were elucidated. Based on the original water inrush coefficient, improved water inrush coefficients corresponding to various faults were developed. Using mining face 81501 of the Liangzhuang Coal Mine in the Xinwen Coalfield of Shandong Province as an engineering case, the accuracy of the water inrush coefficients corresponding to non-penetrating and penetrating faults was verified through field measurements and numerical simulations, respectively.

Results and Conclusions The improved water inrush coefficients comprehensively consider multiple factors, including the water yield property of aquifers, the lengths and dip angles of faults, the depth of the hydraulically conductive fractured zone in the coal seam floor, the thickness of the relative aquiclude, and the width of waterproof coal (rock) pillars, enhancing the scientific rigor and accuracy of the risk assessment of floor water inrushes in areas with faults. Compared to the original water inrush coefficient, the water inrush coefficients corresponding to non-penetrating faults increased by approximately 50%, with the high-risk zones identified proving highly consistent with actual water inrush locations. The water inrush coefficients corresponding to penetrating faults increased by approximately 158%, with the water inrush zones determined through assessment aligning with numerical simulation results. Overall, the improved water inrush coefficients allow for more rational and accurate risk assessment of floor water inrushes in areas with faults, providing a theoretical basis and technical reference for the prevention and control of water hazards in mines with similar geological conditions.