Study On Mechanism Of Spalling In Longwall Face Of Large Mining Height In Shallow Coal Mines

The large mining height of fully mechanized is one of efficient methods of thick seam. Inrecent years, with the increase of mining height, spalling problems and supporting costs andother series issues have become increasingly prominent, the coal wall stability and the load ofsupport is still need to research systematic. This article use the geological data of Bu Lian-talarge mining face as background, based on analyzing the measured data of pressure behaviorin different mining height faces, and use numerical calculation, physics simulation andtheoretical analysis to research the interaction between “support and surrounding rock” andrevel the spalling mechanism of large mining height, to provide basis for determining thereasonable support resistance.Using UDEC numerical calculation software and according to the mining condition ofBu Lian-ta working face22303, and established numerical model of4.0m,5.0m,6.0m,7.0m.Found the breaking position of roof in larger mining height shallow seam have three scenarios,the roof breaking position occurred in the rear support, above the coal wall and in front ofcoal wall. the stress distribution of the immediate roof is different under various conditions.Therefore we can divided the immediate roof into different zones in the transverse. Obtainedspalling characteristics and stress distribution regular of coal wall in different mining height,analyzed the relationship among mining height, support pressure and the width of plastic area.the coal wall “vertical slice” failure feature is found, and the vertical slice mechanical modelwas set up. Through the analysis of deflection of the vertical slice mechanical model, the mosteasily spalling position is at the0.60times of mining height, and put forward the controlmeasures for coal wall spalling.Through analyzing the supporting system of “coal wall+support–immediate roof–main roof”, and analysis of the interaction relationship of the “spalling-support resistance”, and established structural modes of “main roof–immediate roof–support”, and alsoanalyzed the relationship between support working resistance and coal wall stability. Finally,given out the formula of support resistance.