## 3 Materials and Methods  
### Grouting Effect Evaluation Index System  
The evaluation of grouting effectiveness involves assessing the success of water plugging or reinforcement achieved through grouting using specific technical methods, followed by a hierarchical analysis of the results. This allows for timely intervention in weaker areas to ensure the safe operation of coal mines. The selection of appropriate evaluation indicators is particularly crucial in this process. One of the key indicators is the final grouting pressure [25; 26], which serves as a critical benchmark for determining whether a grouting section meets the completion standards. The final pressure significantly influences both the extent and quality of the grouting fill rate. During the grouting process, slurry infiltrates and compacts fissures under the applied pressure, and the final grouting pressure plays a vital role in controlling fissure compaction. This parameter is essential for maintaining the stability of the rock mass during and after the grouting process. A well-calibrated final pressure ensures a high-quality grouting outcome, while excessive pressure risks widening fissures, potentially leading to rock destabilization and structural damage. In practice, the volume of grout used has been shown to provide some indication of the grouting effect [27; 28]. However, the relationship between grout volume and effectiveness remains ambiguous, as grout consumption is heavily influenced by the geological structure at the grouting site. Consequently, it is difficult to quantitatively assess grouting performance solely based on grout volume. Drawing from coal mine water control practices, the amount of dry material per unit length is often employed as a more reliable indicator. Generally, for a given surge volume, a higher dry material volume per unit length is indicative of a more effective water-plugging outcome. The grouting transformation of aquifers is aimed at preventing sudden water surges in mines. Some researchers suggest that the permeability of geotechnical materials can serve as a critical reference for assessing the likelihood of sudden water events [29; 30]. The key indicator of permeability is the permeability rate, which quantifies how easily water can pass through a material under normal atmospheric pressure. A lower permeability in the grouted rock body indicates reduced water flow capability, thereby enhancing its water-blocking effectiveness. Thus, the lower the permeability, the greater the rock body's ability to isolate water and prevent flooding. During the grouting process, drilling fluid consumption can also provide a quantitative measure of the grouting effect [31; 32]. High drilling fluid consumption reflects a more complex geological structure in the coal seam base, suggesting the presence of dense faults or karst fissures in the overlying strata. In contrast, lower fluid consumption indicates a simpler geological structure. The complexity of the geological formation affects the difficulty and requirements of the grouting process--more complex formations demand a higher level of precision and pose greater challenges to successful grouting, which can impact the final grouting effectiveness. The grouting process was carried out in layers, targeting the bottom boundary of the wind-oxidized zone, the upper and lower sandstones above the 9-coal roof (March-May 2023), and the four ash layers of the Taiyuan Formation (June-July 2023). Considering the specific conditions at Banji Mine, four variables have been selected as key indicators for evaluating grouting effectiveness: drilling fluid consumption, final grouting pressure, water permeability, and dry material per unit length. The final pressure and dry material per unit length are measured directly at the grouting station, drilling fluid consumption is recorded during drilling operations, and water permeability is determined through on-site hydraulic pressure testing.