Risk assessment of water inrushes from bed separations in Cretaceous strata corresponding to different excavation lengths during mining in the Ordos Basin

Evaluation of the risk of bed-separation water inrush (BWI) hazards in Cretaceous strata is required for safe mining in the Ordos Basin, China. In this paper, three coal mines in the Ordos Basin were selected for detailed evaluation of the water inrush risk. The multifactor superposition method and stress balance arch theory were used to obtain the water inrush risk in the mines from bed separations at different excavation lengths. First, the related BWI factors were analyzed, and the BWI risk index at any coordinate point in the study area was calculated using multifactor superposition. The weights of relevant factors were obtained using the entropy weight method. Then, based on stress arch theory, the overall BWI risk index in the bed-separation zone corresponding to any excavation length was calculated. Finally, the boundary values between different risk levels were obtained by comparing the overall risk in the mining area with and without BWIs. With the help of these boundary values, the overall BWI risk in bed-separation zones corresponding to any excavation length in some mining areas was evaluated. The evaluation results were verified in practice, which demonstrated the scientific basis for and practicality of this BWI risk assessment method.