Experiment study on primary roof falling of fully-mechanized top coal caving mining face with hydraulic fracturing control

in order to solve a long primar fallig span problem of the main roof in the fully-mechanized top coal caving mining face,the paper had a theoretical analysis on the factors fiecedtothe primay allig span of the main oo in the tul-nechanized top coal caing mining face. In No.2306 cal mining face of Zhangcun Mine,the hydrauli fracturing technology was applied to the sie pre-fractring trailfor th inta mining. With the montoring on the coal borehole stress.deformaion of te pilot support gateway cylinder pressuwe and working resistanceof the powered suppot in the coal mining face as well as the comparison analysis on the borehole surrounding rock structure before and afefr the hydrauli fracturing the concusion was made as th fllows.Afer the fracturing operation,the breaking and crack development of he roof surounding rock were remarkably expanded and the fracturing destroyed the integralty of the roofsurounding rock and ffectivly weakened the roof rck stata. The monitoring of the borehole stress mater showed that the hydraulic pre-racturing fect was excellnt and could eff ctively reduce the plot suppot stressof the coal mining face. The monitoring of the surace surrounding rock showed that the defomation ofthegateway was small and the convergence between the t vo sidewalls and between the roof and foor was no change. The continued montoring of the powered supr cyinder pressue and powered support working res itance showed that after the fracturing operation ,the primar falling span of the nain roo in the coal mining face was 15.5 m and 6 m advance tan the basting pre-rcuing frctof the coal mining face under the sinilr conditon. The primary rof raing technology of th full -mechanized top coal caving mining face withthe hyrault fracturing control would have a small engineering workload,high safety,fast construction speed,good roof control effect and othe features and could effectively solve the long pri mary falling span of the main roof and the high powered support pressure of the fully-mechanized top coal caving mining face with the hard roof.