Prediction model of fracture depth and water inrush risk zoning in deep mining coal seam floor

The research on the prediction model of fracture depth in deep mining coal seam floor in China is of great significance to the prevention and control of water disasters and gas extraction in coal mine. However, the previous research on the depth of the damage of the floor has mainly focused on the shallow and medium-deep coal seam mining areas, while less research has been conducted on the deep mining condition. In particular, there is no suitable model for predicting the depth of damage to the floor under deep mining conditions. Therefore, to explore the safety and feasibility of deep coal seam floor mining in north China coalfield, this paper takes the coal seam mining in Pingdingshan coal mine as the engineering background, combines the comprehensive column data of the mining area, and carries out simulations through FLAC^3D to analyze the influence law of mining length, mining depth and mining height on the depth of floor fracture, obtaining the fitting formula of the influence of rock mass disturbance on the depth of floor fracture, which is suitable for the mining floor of the deep coal seam floor of Pingdingshan coal mine. In addition, the comparison and analysis with the measured values of the fracture floor depth in deep mining coal seam floor of eight mines in North China type coalfield show that the fitting formula has stronger prediction ability, higher prediction accuracy and smaller error range, and is more suitable for the practices of coal mining face water disaster prevention and control site for the coal of Group Ji, Group Geng and the strata of the lower protective layer with the buried depth of more than 800 m in Pingdingshan coal mine. In the absence of on-site measurement, the prediction data can be provided for the fracture depth of mining coal seam floor in Group Ji, Group Geng and lower protective layer rock with the burial depth of Pingdingshan coal mine greater than 800 m. Based on the prediction model of the fracture depth of the floor, a contour diagram of the water inrush coefficient of the coal seam floor under these working conditions of 120 m and 200 m mining width with and without considering the floor damage depth is given. It provides better technical parameters for water prevention and control for the reasonable design of the working face and mineable area of the deep mining coal seam floor in Pingdingshan coal mine, which is conducive to the layout of mining areas and the selection of reasonable mining width, and provides a new prediction model and evaluation method for the prevention and control of water disasters in floor caused by the deep pressure mining of coal resources in similar mines in North China coal fields.