Seepage diffusion and application of advanced grouting in Kilometer-deep mines

Liu Zhengmao; Chen Yan; Li Hu; Liu Qingbo; Zhang Zhiliu; Zhu Yangtao; Meng Qingbao; Li Shuai; Zong Chengbo; Wang Jiahao

doi:10.16186/j.cnki.1673-9787.2024040033

Abstract：Objectives Rib failure and roof collapse in deep,soft-rock coal faces under ground pressure are addressed through investigation of seepage diffusion laws and field application of advance grouting for kilometer-deep mining.Methods Taking the 140504 working face of Kouzidong Mine as a case study,a fan-shaped grouting hole layout is designed for advance roof reinforcement with cement slurry.Using COMSOL Multiphysics,the variations in slurry diffusion radius and grouting pressure over time under double-hole grouting are simulated.FLAC3D is then employed to compare the vertical displacement of the surrounding rock before and after grouting,thereby evaluating the reinforcement effect.Results The results show that:(1)the slurry diffuses concentrically,with the highest concentration at the grouting hole,decreasing axi-symmetrically outward;the diffusion radius increases nonlinearly with time.(2)The maximum diffusion ra-dius is attained after 17 h of grouting.By varying the final hole spacing based on this radius,three rein-forcement scenarios—overlapping,tangent,and separated diffusion zones—are simulated;the tangent con-dition is adopted to determine the optimal grouting hole spacing.(3)The grouting pressure remains nearly constant near the injection point,then drops sharply and stabilizes symmetrically toward both sides.(4)Simulation indicates that roof grouting reduces the maximum vertical displacement by 21.4%,demonstrat-ing effective control of overlying-strata movement.(5)Field practice confirms that grouting reinforcement significantly reduces personnel requirements and increases the monthly face-advance rate by 62.4%.Based on actual grouting data,the final hole pressure should be no less than 8 MPa.Conclusions The findings provide a practical reference for the design and implementation of advance grouting reinforcement in kilometer-deep coal faces.