Relative impermeability and hydrogeological characteristics of Ordovician limestone of coal mine in karst spring basin

The hazard of Ordovician limestone karst water is the key threat of deep mining in north China type coal field, the main reason of which is the complicated hydrogeological environment. The lithology of Ordovician top, the development characteristics of karst fissure and the relative water abundance are studied in detail by means of drilling, hydrogeological tests and transient electromagnetic exploration. The relative impermeability of Ordovician top is presented. Single well pumping test and multiple well pumping test are conducted and the characteristics of seepage field of the aquifer is found out. The hydrochemical field and its evolution law are discussed deeply by the water chemical analysis. The general evolution sequence of karst water quality type during the run-off path is HCO3 → HCO3 · Cl → Cl. The study zone is divided into run-off partitions by hydrochemical field, which indicates that the field Ordovician limestone aquifer is located in weak flow and stagnant regions. The general principles are put forward based on the hydrogeological characteristics of field Ordovician limestone aquifer, including reasonable depth and convenient implementing, first geophysical exploration and target outlining, hydrographic system construction and monitoring detection following, upstream drilling and guiding grout, effects guaranteeing and paying attention to environmental protection. This study provides some guiding significance for preventing and controlling of Ordovician limestone karst water hazard under deep mining condition and the reform of Ordovician limestone aquifer.