Taking a coal mine in the Weibei Mining Area of Shaanxi Province as the engineering background, and focusing on the floor water inrush problem encountered in the mining of narrow strip working faces above the Ordovician limestone confined aquifer, this study effectively overcomes the limitations of the traditional high-cost surface large-scale aquifer grouting reconstruction technology and the discontinuous underground short-hole aquifer grouting reconstruction technology, and proposes a continuous underground directional long-borehole grouting reinforcement technology targeting the aquifuge. A comprehensive research methodology integrating theoretical analysis, numerical simulation, and field measurement is adopted to systematically investigate the pore structure characteristics, mining-induced failure mechanism, water richness and grouting reinforcement effect of the coal floor. The results show that the permeability of quartz sandstone ranges from 0.033 to 0.059 mD, and its porosity varies from 1.926% to 7.776%. Notably, scanning electron microscope (SEM) observations reveal that abundant micropores, mesopores and distinct fractures are developed inside the rock, endowing it with certain seepage capacity. Under the condition of narrow strip mining, the maximum failure depth of the floor is approximately 5.74 m, with shear failure as the main failure mode. The rock strata within the range of -6.5 m to -15.5 m below the floor are basically unaffected by mining activities and exhibit favorable water-resisting performance. Therefore, based on the floor failure depth, water-resisting performance, and pore structure characteristics, the grouting reconstruction horizon is arranged within the quartz sandstone layer. Finally, grouting reconstruction of the target horizon was carried out using underground directional long boreholes, which significantly improved the apparent resistivity of the rock mass. This confirms that the continuous grouting technology can effectively seal fractures and pores and enhance the performance of the target aquifuge. The research results provide a new approach for the prevention and control of water hazards in mine floors under similar conditions.
Ma et al. (2026) studied this question.