Research on Structure Transformation Characteristics for Immediate Roof Key Strata with Large Mining Height

For the characteristics that immediate roof key strata structure has larger influence on strata behaviors in fully-mechanized caving stope, the criterion of immediate roof key strata "cantilever beam" structure is established. 8202 fully-mechanized caving face with large mining height in Jinzhuang Coal Mine is taken as an example to carry out calculation analysis and on-site verification. Results show that immediate roof key strata of thick coal seam fully-mechanized caving stope can generate "cantilever beam" structure. Under the protection of immediate roof key stratum "cantilever beam" structure, the lower direct roof is compacted and lagging; with the advancing of working face, immediate roof key stratum structure transfers to hinged structure, and presents "cantilever beam" structure, hinged structure alternately.