Abstract
In coal seam mining, the water resistance of the floor composite strata is the key to determining whether water disaster occurs or not and to formulating water control countermeasures. Taking the Pingdingshan Coalfield No. 8 mine and Shoushan mine as the research objects, the thickness ratio of plastic brittle rock, core recovery rate, thickness of effective aquiclude, fault complexity, composite compressive strength, and equivalent water resistance coefficient were selected as the index factors. The comprehensive weight of each index factor was determined by using the entropy weight theory. The water resistance of the J16-17 coal seam floor composite rock in the study area was quantitatively evaluated using the fuzzy variable set mathematical model and was divided into five grades: extremely weak, weak, medium, strong, and very strong. The results show that the J16-17 coal floor composite rock layers with strong and very strong water resistance areas account for 23.64% of the total area, the medium areas account for 58.26%, and the weak and extremely weak areas account for 18.1%. These results provide support for the accurate assessment of water inrush hazards of a coal floor.
Highlights
In the process of mining Permian Carboniferous coal seams in North China coalfields, water inrush from an Ordovician or Cambrian thick limestone aquifer is always a threat
Between the coal seam and thick limestone is the barrier for resisting high water pressure and preventing groundwater from rising. It is of great theoretical and practical significance to quantitatively evaluate the water resistance capacity of the composite rock strata, which can scientifically formulate water prevention and control countermeasures to reduce the degree of harm from water inrush in an area
Yang [3] believed that the essence of mining under pressure is the existence of combined water, which makes the rock strata have the ability of water resistance and decompression, and proposed the concept of water resistance coefficient
Summary
In the process of mining Permian Carboniferous coal seams in North China coalfields, water inrush from an Ordovician or Cambrian thick limestone aquifer is always a threat. Lyu and Xie [13] and Zhang et al [14] used statistical analysis and laboratory experiments to study the lithologic combination characteristics, rock mechanical strength, water properties, and permeability of coal seam overburden rock and evaluated the comprehensive water resistance capacity. The research on the water resistance capacity of rock layers has developed from the initial consideration of a single factor such as rock thickness or lithologic difference [16,17,18,19,20] to a comprehensive analysis of multiple factors such as lithology combination, rock mass strength, and permeability, making the evaluation system more and more perfect. The research results are expected to provide technical support for an accurate evaluation of water inrush risk from coal floors
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