## 2 Engineering Geological Background  
The Renlou Coal Mine is situated at the junction of Suixi and Mengcheng counties in Huainan City, Anhui Province, on the southeastern edge of the North China Platform. The primary coal-bearing strata are Carboniferous-Permanic formations. The immediate roadway roof consists of mudstone, with an average thickness of 1.87 m, while the overlying stratum is water-bearing fine sandstone, with an average thickness of 5.68 m. The sandstone layers within the roadway contain aquifer zones, with a normal water inflow ranging from 0 to 11.8 m\({}^{3}\)/h and a maximum inflow of up to 20 m\({}^{3}\)/h. The presence of water has weakened the mechanical properties of the surrounding rock, leading to a decrease in the self-bearing capacity of the anchoring system and a reduction in roof strength. Under actual conditions, the hazards of mine water can be identified by monitoring the chemical indicators of mine water, such as the pH value, TDS (Total Dissolved Solids) concentration, dissolved oxygen level, and flow velocity, to observe the corrosion status of anchoring materials. In addition, the geological conditions can be used to analyze the reactions of minerals with water and oxygen [34]. The roof wetting conditions at the site, along with a comprehensive column chart of the roadway's roof and floor, are illustrated in Figure 1.  
The weakening mechanism of the roof rock strength under water-rich conditions is illustrated in Figure 2.  
As Figure 2 shows, the roof of the roadway comprises a sandstone layer overlaid by a water-bearing aquifer. The moisture in this aquifer gradually infiltrates downward into the underlying sandstone layer through percolation, causing significant weakening of the surrounding rock. As the roadway construction progresses, the stress state within the surrounding rock undergoes a marked change [35; 36], which is clearly depicted in the stress variation curve shown in the figure. Within the area affected by the roadways, stress concentration zones have developed in the roof and sidewall regions. To enhance the  
Figure 1: Water inflow into the roadway roof. Figure 2: Schematic diagram of roadway roof degradation under water-rich conditions. roadway stability, rock and cable bolts were installed on the roof for support. However, owing to the presence of a water-bearing aquifer in the sandstone layer of the roof, water has infiltrated the boreholes of the bolts, forming new water-conducting pathways that have further intensified the water-rock interactions. The formation of new water-conducting pathways has resulted in the expansion of internal fractures, significant strength degradation, and a marked reduction in the shear resistance of the rock. Continuous water infiltration has caused the sandstone layer to gradually transition from the elastic deformation phase to the plastic deformation phase, accompanied by rapid fracture development and expansion. During this process, the sandstone layer of the roof has undergone substantial deformation, which has manifested as a noticeable subsidence of the roadway roof, with inward displacement of both sidewalls and bulging of the floor. The subsidence of the roof and displacement of the sidewalls have exacerbated the damage to the surrounding rock, resulting in a significant decline in the overall stability of the roadway. To further understand the rock properties of the sandstone in this area, a thin-section analysis of the water-bearing sandstone was conducted, as shown in Figure 3.  
According to the identification results provided by the Hubei Geological Laboratory (Figure 4), the water-bearing sandstone is a fine-grained rock; the structural type is fine sandstone, with the main components being quartz, feldspar, lithic fragments, and a matrix content of 20%. Microscopic observation revealed a homogenous microstructure influenced by compaction and recrystallization processes.