Effect examination of advance regional management of water hazards in ultra-thick loose layers of coal mine roofs

YAN Xin; DING Xiang; PU Zhiguo; LI Zhe; FENG Jie; JI Zhuochen

doi:10.11799/ce202508010

Abstract：Aiming at the problem of lacking effective inspection methods for the grouting treatment effect in water hazard areas of ultra-thick loose layers,a surface-underground multi-index stereoscopic inspection method is proposed.This method evaluates the effectiveness of grouting treatment in coal seam roof by analyzing subsequent borehole cuttings logging,core observation of grouted horizons,and comparative analysis of parameters such as aquifer water levels before and after grouting,underground water drainage volume,formation permeability,and the grout connectivity of underground boreholes.The results indicate that the planar diffusion distance of the grout ranges from 31.68 to 64.85 meters,while the vertical diffusion distance exceeds 30 meters,as determined by the distribution of clay-cement grout blocks and fluorescent tracers in subsequent boreholes,inspection boreholes,and core samples.No abnormal consumption of drilling fluid was observed in the inspection boreholes,suggesting that the formation structure within the treated area remains relatively intact after grouting.The grouting volume required for verification boreholes was significantly lower than that for treatment boreholes,demonstrating effective grout filling achieved by the initial treatment.Grouting in verification boreholes did not cause fluctuations in aquifer water levels,and no grout connectivity was detected underground,indicating that the original vertical water-conducting channels have been effectively sealed.Following the completion of grouting,both the water inflow volume and the number of water-producing boreholes during dewatering tests underground decreased markedly.This confirms that the hydraulic connection between the"Fourth Aquifer"and the sandstone aquifer above the No.9 coal seam has been effectively blocked,achieving the intended grouting objectives and ensuring safe mining conditions for the working face.