Characteristics of mine aquifer with complex structure and identification of its hydraulic connection

Five groups of aquifers are developed in the mining area of the Beixinyao coal mine, Ningwu, Shanxi Province. Complex fault structure leads to unclear hydraulic connection of various aquifers in this coal mine. Thus, it is difficult to identify the water inflow sources and further put forward some targeted water prevention measures. Based on the tracer characteristics of hydrogen and oxygen isotopes, tritium isotopes and 14C isotopes, and combined with the test techniques of conventional hydrochemical ion characteristics and trace elements, the hydraulic relationship of each aquifer was analyzed. The water quality characteristics and hydraulic relationship of each aquifer in the Beixinyao coal mine were determined. A comprehensive discrimination method for hydraulic connection of multi-layer aquifers under complex hydrogeological conditions was proposed. The three identification charts (Piper and Durov identification charts of conventional hydrochemical components and deuterium tritium isotope identification charts) established can realize the rapid identification of aquifer water sources. The hydrogen and oxygen isotopes analysis shows that there is a hydraulic connection between the Shihezi Formation and the Cenozoic aquifer, and between the Taiyuan Formation, the Shanxi Formation and the Ordovician aquifer. Tritium isotope tracing can determine that there is a hydraulic connection between the Shihezi Formation aquifer and the Cenozoic aquifer, between the Taiyuan Formation and the Shanxi formation, and between the Taiyuan Formation and the Ordovician aquifer. The 14C isotope tracing shows that there is a hydraulic connection between the Shihezi Formation aquifer and the Cenozoic, and the Shanxi formation, the Taiyuan Formation and the Ordovician aquifer are mixed with each other. Combined with the characteristics of conventional hydrochemical ions and trace elements, it is finally determined that the Ordovician limestone water has a hydraulic connection with the groundwater of the Taiyuan Formation and the Shanxi Formation. The Ordovician limestone water flows over to recharge the two aquifers above it. The Cenozoic is hydraulically connected with the Shihezi Formation and supplies the aquifer of the Shihezi Formation.