The Strata-pressure Behavior Research Of Repeated Mining Face Under Thick Coal Seam Upper Layered Goaf Areas

For the repeated mining of remaining coal resources on thick coal seam upper layered tool pillar areas,the strata-pressure behavior exists particularity due to the complex structure of overlying strata and it would impact the mine safety and efficient production.By taking thick coal seam repeated mining face influenced by the old coal mine mining damage on the Datong Coal Mine Group Huasheng Hufeng Coal Limited(mine)as the research object,this article makes full use of theoretical analysis,numerical simulation and field measurement to study the strata-pressure behavior characteristics on repeated mining face.The main conclusions are as follows:(1)According to the actual situation of coal pillars in Hufeng mine goaf,the extended SMP damage failure criterion is used to study the stability of coal pillar on the basis of research on the distribution characteristics of stress of coal pillar and the method to judge the stability of coal pillar is obtained.(2)Basing on study on stability of coal pillars,the stability of goaf overlying strata is studied.Through the analysis of the failure mechanism of basic roof,amethod for judging the failure of the basic roof is obtained with combining the thin elastic foundation theory and cusp catastrophe theory;meanwhile using the slip line field theory to analysis damage situation of bottom coal,the failure depth of coal bottom is obtained.(3)Considering the method of theoretical calculation,numerical simulation and field measurement synthetically,the roof weighting step and the ground pressure strength are analyzed and calculated.The rules of strata-pressure behavior on repeated mining face are obtained:when repeated mining face passes thick coal seam upper layered coal pillar,the abutment pressure of repeated mining face shows a law of “weak-strong-weak ”;while repeated mining face passes thick coal seam upper layered goaf,the abutment pressure of repeated mining face would be different according to the size of the goaf.when the size of goaf is small,the abutment pressure of repeated mining face shows a law of “strong-weak-strong ”;when the size of goaf is large,the abutment pressure of repeated mining face shows a law of“strong-weak-strong-weak-strong ”.(4)Combining the above research results with the actual situation of mining work face,the key factors of mining working face surrounding rock control are analyzed and the method of mining working face surrounding rock control are also researched from two aspects:the stope support and other ways of mining working face surrounding rock control.