Study On The Dynamic Change Law Of Water Inflow In Coal Seam Repeated Mining Mines And The Utilization Of Mine Water Resources

During coal mining,a large amount of wastewater is generated and discharged.For a long time,due to technical or condition constraints,a large amount of mine water has been discharged as wastewater,damaging the local ecological environment,while also wasting a large amount of water resources and increasing the production cost of coal mines.In recent years,with the development of technology and the emphasis on water resources,the efficient utilization of mine water resources has gradually received attention.Taking NL coal mine in northern Shaanxi Province as an example,based on field exploration,combined with simulation experiments,mathematical statistics,theoretical analysis,and other methods,this thesis focuses on studying the dynamic change rules of mine water inflow and water quality caused by coal seam roof damage under repeated mining conditions,and designing efficient utilization plans for mine water,as well as exploring the economic and ecological benefits that can be achieved.The main research results obtained in the thesis are as follows:（1）The study revealed the dynamic law of water inflow in the NL mine.The water conducting fracture zone formed under repeated mining conditions in multiple coal seams will become the main water filling channel of the mine.Therefore,under conditions such as the old goaf water after mining in the 3^-1 coal seam,and partial regional atmospheric rainfall indirectly participating in the mine water inflow through infiltration to recharge the lower aquifer,the mine water filling intensity increases.（2）Comprehensive research has been conducted on the failure law of overlying rock during repeated mining of multiple coal seams and its impact on the dynamic change mechanism of mine water inflow.Using FLAC3D,the high development height of the water conducting fracture zone in the mining of coal seams with and without overlying 3^-1 coal seams was simulated,and it was concluded that repeated mining of multiple coal seams would greatly increase the development height of the water conducting fracture zone,destroy the overlying multi-layer aquifer system,and even form an effective water filling channel connecting the surface to the underground,increasing the risk of water inrush in the mine.At the same time,repeated mining disturbances worsen the quality of mine water inflow,increasing the difficulty of efficient utilization of mine water inflow.（3）A neural network model was established to comprehensively predict the mine water inflow mechanism after repeated mining.Establish a PCA-BP neural network model to predict the water inflow of the mine,select the main factors that affect the water inflow of the mine for principal component analysis,and obtain that the water inflow of the mine is most significantly affected by the monthly development of the roadway and the cumulative roadway development length.It is predicted that the average water inflow of the mine in the next year is 33.15 m³/h.Based on the PCA-BP neural network model,a Piper-PCA-BP neural network model was established to analyze the source types of mine water,and PCA analysis was conducted on the main ionic components contained in different types of aquifer water in the mining area.The seven factors affecting the hydrochemical types were reduced to three main influencing factors,and the three principal component factors after the reduction were brought into the BP neural network for type classification,it is obtained that two types of water,namely,the sandstone fissure confined water of the Middle Jurassic Yan’an Formation and the Quaternary Upper Pleistocene loess fissure pore water,are the main sources of mine water inflow.（4）Based on the above,the dynamic change mechanism of mine water inflow under repeated mining conditions in multiple coal seams is summarized.Repeated mining in multiple coal seams has led to an increase in the types of water filling sources in the mine,an increase in the amount of water inflow in the mine,and a more complex and diverse water filling channel.The superposition of 3^-1 coal and 2^-2 coal water conducting fracture zones has led to a significant increase in the development height,the size and number of fractures,the opening degree,and the distribution range of the water conducting fracture zone.At the same time,due to the changes in water inflow sources,water inflow channels,and the more complex interaction between water and rock,the ion composition of mine water inflow quality is more complex,and the p H value is reduced.（5）Based on the actual situation of NL coal mine,a comprehensive design for efficient utilization of mine water was conducted and the possible benefits were analyzed.According to the importance of factors affecting the water inflow of the working face,the working face is divided into different levels of controlled drainage areas to achieve accurate controlled drainage of the mine water.PLC underground water intelligence detection system is designed to monitor the underground water inflow status,and achieve the underground clean and sewage diversion of the underground mine water.The water with good quality after the clean and sewage diversion is applied to underground production and life after simple underground treatment,The mine water with relatively poor water quality is transported to the surface water treatment station for treatment and then used for production and living in the mining area to reduce the demand for external water purchased by the coal mine and save the production cost of the mine.