Key technology and equipment for fully mechanized mining with extra-large shearing height of 10 m in extra-thick coal seam

Fully mechanized mining technology with extra-large shearing height is the optimal technical approach to achieve high-yield, high-efficiency and high-recovery mining for 6−10 m ultra-thick coal seam in Chinese coal mines. Based on the analysis of the current status of fully mechanized mining technology and equipment with extra-large shearing height at home, focusing on the geological condition of fully mechanized working face with ultra-large shearing height of 10 m in extra-thick coal seam in the Caojiatan Coal Mine, Shaanxi Coal and Chemical Industry Group Co., Ltd., the existing technical problems were analyzed and the associated solutions were given from three aspects: surrounding rock control, key mining equipment and intelligent collaborative control. After nearly five years of scientific research, a series of innovative achievements have been achieved: ① The surrounding rock control strategy with coordination of support and destressing for ultra-large shearing height working faces, namely “active strong support and protection + regional hydraulic fracturing weakening and stress relief”, was proposed, a complete set of underground hydraulic fracturing technology and equipment with large flow of 5 m3/min was developed. Effective prevention and control of strong mining-induced activities in ultra-large shearing height working face has been realized. ② The strong hydraulic shields with ultra-large shearing height of 10 m were developed, and the “double-layer telescopic beam + three-level side guard” mechanism was innovatively designed to achieve safe protection of working face roof and ultra-high coal wall; the zoned lubrication and distributed cooling scheme improves the cutting reliability of the shearer with large angle of elevation and long rocker; the high-reliability middle trough, lower chain catenary and slow-changing power start-up improve the adaptability of the ultra-large capacity scraper conveyor to the coal flow transportation of the working face with ultra-large shearing height. The systematic integration has formed the global first set of comprehensive mining equipment with extra-large shearing height of 10 m. ③ An innovative intelligent control strategy for the operation status of the hydraulic shields with 10 m ultra-large shearing height, and the automatic control strategy for the shearer were proposed. A coordinated control system for the shearer with ultra-large shearing height and the scraper conveyor was constructed by applying the rough neural network technology. An intelligent control mode and control logic for heavy equipment groups with ultra-large shearing height were formed. ④ A multi-field and multi-parameter collaborative monitoring and integrated analysis system for the working face with ultra-large shearing height based on “microseism-rock movement-stress-hydrology” was constructed, realizing the multivariate heterogeneous data integrated analysis among damage of overburden rock above working face, surface movement and deformation, groundwater flow field and mining-induced activities. The research results were successfully applied in the in Caojiatan Coal Mine, achieving high-yield, high-efficiency and high-recovery mining in 10 m ultra-thick coal seam, getting significant economic benefits, and leading the development direction of high-efficiency and intelligent mining for extra-thick coal seam at home and abroad.