Hydrochemical Characteristics Of Ordovician Limestone And Numerical Simulation Of Groundwater Flow In Tangjiahui Mine

Taking the Ordovician limestone water in tangjiahui mine of Jungar coalfield as the research object,the hydrochemical characteristics,formation mechanism and evolution of Ordovician limestone are studied by using the methods of hydrochemical index statistical analysis,spatial distribution isoline map,Piper diagram,ion proportion coefficient and statistics.By analyzing the dynamic change curve of Ordovician limestone water level in the study area,the evolution characteristics of Ordovician limestone water flow field are revealed,and the dynamic influencing factors of Ordovician limestone water level are analyzed from three aspects:mining disturbance,hydrogeological conditions and recharge.The numerical model of Ordovician limestone water flow is established to simulate and predict the flow field of Ordovician limestone water in the study area under future mining conditions.The main research results are as follows:（1）The Ordovician limestone water is characterized by"low salinity and high Cl^-".The Ordovician limestone water is type Cl-Na.The ion content,mineralization and total hardness increase gradually from north to south.The minimum value appears at the supply boundary in the northeast of the mine field and the maximum value appears at the discharge boundary in the southwest.（2）The chemical components of Ordovician limestone water in the study area are mainly controlled by water rock interaction.The ion components of Ordovician limestone karst water are mainly formed by the leaching release of minerals such as rock salt,the alternating adsorption of cations and the oxidation of sulfides such as Shanxi style iron ore（Fe S₂）.（3）From 2015 to September 2021,the groundwater level of Ordovician limestone observation hole in the study area decreased by 2.63～11.08 m,The decline rate of Ordovician limestone water level in the first mining area is significantly higher than that in the area with less mining area.The water drainage in Ordovician limestone mining area is mainly controlled by the abnormity of water drainage in Ordovician limestone mining area.Faults and geological abnormal bodies are the main channels for the Ordovician limestone water to flow into the roadway;The main reason for the slight rise of Ordovician limestone water level is the atmospheric precipitation and the lateral recharge of karst water by Yellow River water.（4）Combined with the next mining plan of the South Panel II of the mine,the Ordovician limestone water level is predicted according to the established groundwater flow numerical model.The results show that the Ordovician limestone water level in the study area is between 852.0～856.9 m in February 2024.The Ordovician limestone water level in the mine field gradually decreases from northeast to south,and the decline range of water level increases to 7.7～9.1m.The North-South gap of Ordovician limestone water level in the study area continues to narrow.