Study On Overburden Migration Features Of Top-coal Caving Mining And Index Analysis Of Two-zone Height

By having similar material simulation and numerical simulation experiment,taking the geological condition of Zhuxianzhuang mine as prototype,movement characteristics of overlying rock of fully mechanized caving of thick coal seam has been deeply analysed,multi factors analysis has been used to analyse the two zone height of mechized caving,new formula has been obtained.Main contents are as follows.According to geological condtions of Zhuxianzhuang coal mine,similar material simulation has been used to analyse damage and displacement characteristics of a full seam mine by mechanized caving of extremly thick coal seam under thick loose aquifer, height of overlying rock sinking zone and fracture zone develops as step leap style and tends to be stable,sinking height is determined to be16.1m,fracture height is66.3m.With the advacnce of working face,mined out area expands larger and larger,groups of overlying rock start to sink in different degree,maximum subsidence of rock stratas are basically in middle upper goaf,and stress distribution law has been shown during excavation process of working face.Numeral simulation of FLAC has been used to analyse movement characteristics of overlyingrock during mechanized caving,overlying stress,displacement and distribution law of plastic zone has been obtained when working face is advanced in dirrerernt distance.After coal seam has been mine out,overlying rock will generate tensile failure and shear failure in turn from bottom to top, sinking zone and fracture zone will be formed.Height of caving zone has been judged to be16.1m,height of fracture zone is68m.Two zone measured data and relevant parameters of working face has been collected.Hard rock ratio has been put forward to quantitative describe overlying rock property,multiple linear regression has been used to deal with data,extravation thickness,hard rock ratio,burial depth,working face length,five influensce factor prediction formula of dip angle of coal seam about two zone has been obtained.New prediction formula predicts two zone height are bigger than actual measurement value.and error value is smaller than experimental formula,which is more close to actual measurement value,more accurate than experience formula.In order to further verify the reliabillty of formula,two "two zone"spy hole has been arranged in873fully mechanized top coal caving working face of Zhuxian mine.Height of caving zone by actual measurement is11.34-15.74,caving height is1.44～1.69.Error of prediction formula value and actual measurement value is close,and is close to the value obtained by similar material simulation,which futher prove the reliability of the fomula.