14 coal safety mining mainly considers the following aspects:
(1) Quaternary aquifer is the recharge source of several underlying aquifers, which will not directly affect the safe mining of 14 coal. Similarly, the Ordovician limestone aquifer will not directly affect the safe mining of 14 coal.
(2) The fractured sandstone aquifer of coal 12- coal 14 is the confined aquifer of coal 14 roof, which will cause roof caving and water filling during coal mining. However, it can be seen from the West No.1 mining area that this aquifer is a weak aquifer and can be drained. Therefore, the aquifer of coal 12- coal 14 will not pose a threat to the safe mining of coal 14, and drilling can be used before mining.
(3) The coal 14-K3 aquifer is a confined aquifer (group) in which coal 14 mines the sandstone with direct floor, and its fractures are relatively developed, which will directly threaten the coal 14 mining. However, this aquifer belongs to medium aquifer. According to the data of mine water inrush in the past, it can be seen that the 14-K3 coal seam aquifer has a close hydraulic connection with the 12- 14 coal seam aquifer, and the 12-65438 coal seam aquifer can also be dredged to some extent by exposing it. Combined with the prediction of water inflow and the statistical data of mine water inflow, it shows that the water inflow is limited. Therefore, after taking certain drainage and safety measures in mining, the safe mining of 14 coal will not cause serious water damage.
(4)K3 limestone is the indicator layer between the coal 14-K3 aquifer and the Ordovician limestone aquifer, the transition layer and the key layer, and the direct water-filled aquifer that determines the coal 14 mining. Its water-bearing, water-rich and water-blocking properties and its connection with Ordovician limestone water are directly related to the safe mining of 14 coal, which is of decisive significance to the safe mining of 14 coal. Therefore, the hydrogeological conditions of K3 limestone should be comprehensively explored, including water abundance, water resistance and hydrochemical characteristics.
(5) Ordovician limestone aquifer has always threatened the safe mining of deep coal seams, and the mining of 14 coal seam is no exception. From the analysis of hydrogeological data in the mining area for many years, it is found that there is little direct water inrush from the Ordovician limestone aquifer, and the gravel aquifer at the bottom of Quaternary system is replenished mainly through overflow, and then other aquifers below it are replenished. Distance from 14 coal seam floor is about 120m. Judging from the water inrush coefficient, 14 coal seam mining is safe. However, due to the development of karst and cracks in the upper part of Ordovician limestone, high water pressure and abundant water, structural water inrush may occur in the structural area (for example, there was an Ordovician limestone water inrush event on Rudong Line 1, but the reason is unknown). Once water inrush occurs, it will cause great losses to mine production. Therefore, Ordovician limestone aquifer is the key prevention object of 14 coal seam mining.
(6) Fault structures are developed in the mine field, and the drop of some faults exceeds 100 m, which shortens the distance between the mining coal seam and the Ordovician limestone aquifer and increases the probability of structural water inrush and induced water inrush. Therefore, waterproof coal pillars should be reasonably left in the structural parts.
(7) A large number of data show that floor water inrush is generally structural water inrush, so the mining of 14 coal seam must be prevented. Before mining, we should increase the exploration of faults, collapse columns and other structural occurrences in the mining area, and do a good job in floor monitoring, water level observation and hydrochemical characteristics analysis. This paper analyzes the communication and conduction relationship between K3 limestone water and Ordovician limestone water, so as to prevent the sudden water disaster of Ordovician limestone structure.