Surrounding rock control technology of 10 m super large mining height working face in Caojiatan Coal Mine

WANG Rui; XU Gang; KANG Hongpu; ZHANG Zhen; LEI Yajun; FENG Yanjun; MA Ying; HUANG Zhizeng; LIU Qianjin; LIU Xiaogang; LIN Xingyu; MA Rongshan; ZHAO Zhen; LI Zhengjie

doi:10.13225/j.cnki.jccs.2024.1420

Abstract：The 10 m ultra-large mining height of Caojiatan Coal Mine is a world's first in terms of single mining height and mining intensity,and the effective control of surrounding rock in the stope is crucial for safe and efficient mining at the working face.Based on the analysis of the coal seam occurrence conditions and the characteristics of the ground pres-sure behavior of the already mined faces,and considering the ultra-large mining space and the ultra-high coal wall charac-teristics of the working face,the difficulties in controlling the surrounding rock of ultra-large mining height were clarified.A"superimposed arch-beam"structural model for the ultra-large mining height stope was established,and a three-in-one surrounding rock control strategy of"active support protection+regional pressure relief weakening+comprehensive monitoring and early warning"was proposed,verifying the effectiveness of the surrounding rock control for the 10 m ultra-large mining height.The research shows that:the occurrence characteristics of multi-layer thick and hard roofs cause ab-normally strong mine pressure manifestation at the working face,with large-area hanging roofs during initial mining and significant strong dynamic loading pressure at the working face during normal mining.The keys to controlling the sur-rounding rock in the 10 m ultra-large mining height stope are reducing the pressure step distance,weakening the dynamic loading pressure,preventing rib spalling,and preventing the working face from being crushed by the pressure.The"double-layer telescopic beams+three-stage rib protection"structure of the hydraulic support achieves independent opera-tion for the protection of the empty roof in front of the support and the ultra-high coal wall,solving the problem of incom-plete rib protection by the original split-type rib protection.The high initial setting force and high working resistance of the hydraulic support significantly reduce the risk of rib spalling and roof caving at the working face and effectively control the roof subsidence during the pressure period.The underground deep-hole 5.0 m3/min high-flow directional fracturing weakening technology achieves weakening of the multi-layer thick and hard roofs,effectively reducing the intensity of mine pressure at the working face,controlling the amount of rib spalling and significant roof subsidence during the pres-sure period,and preventing the working face from being crushed by the pressure.Comprehensive monitoring and early warning effectively ensures the support efficiency of the support during mining,realizing real-time tracking of roof frac-ture and real-time analysis of strong mine pressure.The problems of large-area hanging roofs and small hurricanes during the initial mining of the ultra-large mining height working face have been resolved.The initial pressure step distance is 49.35 m,the pressure duration distance is 5.75 m,and the opening ratio of the safety valve of the support column is 24.81％.The manifestation of mine pressure during the periodic pressure period has been significantly alleviated.The av-erage shrinkage of the hydraulic support column has decreased from 0.48 m to 0.32 m,a decrease of 33.3％,and the max-imum shrinkage has decreased from 1.88 m to 1.44 m,a decrease of 23.4％.The proportion of the average dynamic load coefficient of the working face periodic pressure greater than 1.5 has decreased from 39.6％to 14％.During normal pro-duction at the working face,rib spalling is within a controllable range,with the amount of rib spalling concentrated at 0.2-0.5 m.The research results have important guiding significance for the control of surrounding rock in ultra-large min-ing height mining.