Study On The Law Of Motion And Structure Characteristics Of Wide Range Coal Roof Of The Jurassic And Carboniferous Mining In Datong Mining Area

It is easy to cause the increase of strata behaviors and seriously affect the normal production on the working face when a large area of hard roof suddenly caving under the conditions of Jurassic and Carboniferous coal mining in Datong Mining area, so the study of the law of motion and structure instability conditions of a wide range coal roof at the Jurassic and Carboniferous mining in Datong mining area have a important practical significance and theoretical value on strata behaviors law and the control of hard roof.Use the method of physical similarity and numerical simulation, study the roof structure characteristics and law of the stress field, displacement field on the process of coal mining. The research shows that the affected depth is about 63 m, the level of influence range is 35~40m, the maximum stress concentration factor is 3.14 of the coal pillar remaining in the Jurassic, it is not synchronous collapse instability of the lower hard immediate roof on the fully mechanized top coal caving coal seam at the Carboniferous, primary fracture length of the main roof is large, and the main roof instability resulting in goaf through of the Jurassic and Carboniferous, roof structure gradually expand for upward, form the “lower composite cantilever beam-upper multi story masonry”, this structure as skeleton of the roof in the Carboniferous coal seam, and play a decisive role on the working face strata behaviors.Through theoretical analysis, determine the roof gradually expand scope, analyze the instability conditions and modes of different structures, and combined with actual production conditions of 8101 working face in Tongxin coal mine, measured the behavior law of mine pressure, the results shows that the first weighting step of lower hard roof and upper sub-main roof is 106 m and 133.5m respectively, periodic weighting step distance is about 17 m of the working face, Compressive strength is strong and weak appear periodically, the strength of periodic alternating are consist of lower hard roof and upper sub main roof breaking, this pressure appearance law is consistent with the theory analysis of “gradual expansion structures” unstable motion. The results of the study have a guiding significance and theoretical value for the law of pressure behaviors and support selection of the Carboniferous coal seam in Datong mining area.