The assessment of the impact of abandoned mine water on the underwater environment is critical for protecting and restoring the groundwater environment. Taking the abandoned coal mining area in the west of Zhangqiu District as the engineering background and comprehensively considering the regional groundwater chemical characteristics data during the wet and dry seasons, the main characteristics of the ions, hydrochemical types, and ion correlations of the abandoned mine water with the regional groundwater components were analyzed using mathematical statistics, correlation analysis, and Piper diagrams. An impact assessment was conducted on the water quality index values of the groundwater monitoring point. Furthermore, this research establishes an evaluation method of abandoned mine water in a regional groundwater environment based on the improved Nemero index method and matter element theory. Overall, the groundwater pH is weakly alkaline in Zhangqiu District. The groundwater Ca²⁺ is the dominant cation, while HCO₃⁻ and SO₄²⁻ are the dominant anions. The main ion concentration during the dry season is slightly greater than during the wet season. The main hydrochemical type of groundwater during the wet and dry seasons is HCO₃-Ca. In addition, there is a correlation between NO₃⁻ and F⁻, which may be caused by human activities. The groundwater environment is classified as level IV and severely polluted.

Seepage characterization from reservoirs is challenging for various environmental and water resource applications. Nonintrusive geophysical methods can achieve excellent detection results, but they cannot provide a quantitative description of the amount of seepage. Integrating geophysical methods with traditional hydrochemical and hydrologic methods enables simultaneous localization and quantitative analysis of heterogeneous reservoir seepage. Ground and waterborne electrical resistivity tomography are used to scan a reservoir under a typical cutoff wall antiseepage system, and the measurements reveal the northern preferential infiltration area. The hydrochemical results reveal that the seepage bypass of the cutoff wall has led to evident ion concentration variations in groundwater near the dam. Based on the geologic stratum information, the typical cutoff wall antiseepage system is divided into three scenarios for numerical simulation to calculate the seepage. The total seepage of the reservoir over 15 months is approximately 7.15 × 106 m3, which is consistent with traditional water budget methods. However, in the northern part of the reservoir, only 27% of the entire dam contributes 77% of the total seepage. All methods have confirmed that the heterogeneous seepage is caused by the absence of an antiseepage seal in the northern region, which should be a primary focus for future monitoring and operational efforts. With the geophysical results undergoing extensive cross-validation, the results from the preceding methods are comprehensively leveraged, effectively lowering uncertainties and overcoming the limitations of geophysical methods in quantitatively characterizing seepage.

Failure characteristics of the coal seam floor above-confined aquifer are key to evaluating the water inrush risk from the floor in the deep mining. At present, based on the analysis of water inrush impact indicators, mathematical evaluation methods are often used to evaluate the water inrush risk of a mining floor. This study proposes a theoretical risk assessment method for water inrush from the floor considering the failure characteristics of the coal seam floor above-confined aquifer. The 11301# coalface in the Wanglou colliery, Shandong Province, is considered as a case study. The mechanical model of the mining floor stress along the coalface inclination direction was established, and the analytical solutions of the vertical, horizontal, and shear stress and floor failure depth were derived. The floor failure mode along the coalface inclination direction is similar to the letter “lying flat-B” and the maximum and minimum failure depth is around 13 and 6 m. Furthermore, the dynamic failure characteristics of the floor during coal mining were simulated. Subsequently, the thickness of the floor key aquiclude was determined and the water inrush coefficient exhibits a certain trend from increasing to becoming stable in the mining process, that is, from 0.05 to 0.08 MPa/m. The analytical solution of the critical water pressure for floor aquiclude failure was derived based on the limit equilibrium theory. That is, the ultimate water pressure 3.9 MPa is greater than the actual water pressure 2 MPa, and there is no floor water inrush risk. Taking these into account, the water inrush risk of the mining floor above-confined aquifer was comprehensively analyzed and evaluated. The findings were deemed to be consistent with the actual mining case.