Evaluation of Water-Richness and Risk Level of the Sandstone Aquifer in the Roof of the No. 3 Coal Seam in Hancheng Mining Area

This study presents a precise and efficient methodology for evaluating the water-richness of the aquifer overlying the No. 3 coal seam in Hancheng Mine. A comprehensive assessment model was developed by integrating subjective and objective weighting through the sequential relationship analysis–entropy value method. This model facilitated the delineation of water-richness zones within the sandstone aquifer of the Shanxi Group associated with the No. 3 coal seam. Five key evaluation indices were selected based on the aquifer’s water-richness index: core recovery rate, thickness of water-rich sandstone, number of sand–mudstone interlayers, sandstone lithology coefficient, and the thickness ratio of brittle to plastic rock. Furthermore, an advanced evaluation model combining set pair analysis and variable fuzzy sets was established to assess the water-richness risk levels across the entire Hancheng mining area. The results reveal distinct spatial patterns in water-richness: the northeastern region exhibits strong water-richness, while the southwestern area is characterized by medium to weak water-richness over a broad expanse. Overall, the No. 3 coal seam in the Hancheng mining area is classified as having a medium risk level of water-richness.