Risk prediction and application of mining in close-distance working faces under aquifers

In view of the water inrush and support crushing problems encountered during mining of close-distance working faces beneath unconsolidated aquifers, we take the No. 10 coal seam working face beneath the “four-water”aquifer in Wugou Coal Mine as the engineering background, aiming to systematically analyze its water inrush risk and propose effective control measures. By combining theoretical calculation, empirical analogy, numerical simulation, and field monitoring, the water inrush risk posed by the “four-water” aquifer to the underlying close-distance working face was predicted. The prediction results show that the development height of the water-conducting fractured zone at the working face is approximately 32.05–55.03 m, indicating that water inrush accidents during mining at this working face were inevitable. To address this problem, grouting modification technology was applied on site to displace and modify the “four-water” aquifer, thereby preventing water inrush accidents at the working face. Field practice results show that during mining, the roof water inflow at the working face did not exceed 1 m³/h and remained within the normal range; the initial weighting interval was approximately 33.35–35.95 m, and the periodic weighting interval was approximately 10.45 m. This indicates that grouting modification of the “four-water” aquifer successfully raised the safety upper limit for close-distance mining of the No. 10 coal seam and effectively avoided the occurrence of water inrush accidents.