Technology and practice of advance regional control for roof water hazards under ultra-thick unconsolidated aquifers

LI Zhe; DING Xiang; PU Zhiguo; YAN Xin; PANG Long; LIU Kaixiang

doi:10.11799/ce202512011

Abstract：The Huainan Coalfield is overlain by an ultra-thick unconsolidated layer,with its basal Quaternary aquifer characterized by significant thickness and high water abundance.The direct water-filling source for the No.5 coal seam roof at Banji Mine primarily originates from vertical and lateral recharge by this aquifer.This subjects the mine not only to severe threats from unconsolidated aquifer roof water hazards but also to risks of strata subsidence and subsequent shaft deformation/failure due to aquifer dewatering.Therefore,ensuring"zero water inflow"from the unconsolidated layer during mining is imperative.To address these challenges,an advance regional control strategy for roof water hazards was proposed,based on directional drilling and long-distance grouting technologies,shifting the control philosophy from passive treatment to active prevention.Before panel extraction,grouting modification was implemented in the vertical water-conducting stratum above the roof water-conducting fracture zone,while a grout curtain was constructed to cut off lateral recharge channels.Numerical simulation verified the reliability of the treated stratum.A flexible quantification index for grouting materials was established,and an optimal flexible cement-clay slurry mix was determined through proportioning tests,effectively reducing the risk of post-mining grout layer failure.Given the absence of a basal aquitard near the unconsolidated layer,a high-pressure grout diffusion control process was developed.Field application demonstrated that this technology successfully severed the vertical and lateral water recharge pathways to the roof before mining.The treated roof stratum remained intact during extraction,achieving the goal of"zero water inflow"from the unconsolidated layer.