Study on the characteristics of strata behavior in shallow seam longwall mining under the room-and-pillar mining goaf

The study focused on shallow coal seam long-wall mining under room-and-pillar goaf by using the theory analysis and field mine pressure observation etc,in Ordos,it holds that upper overburden on the room-and-pillar goaf have composite beam structure in certain caving height range.The upper basic roof structure is fixed beam and the under is cantilever beam,the room-and-pillar mining goaf and the downside strata become the immediate roof.Under cantilever beam is periodically by upper fixed beam gyroscopic moment,the dynamic load transfer to support structure in mining stope by passing through the pillars in room and pillar goaf.Different instability periodicity of upper fixed beam and under cantilever beam will cause weighting length and ground pressure strength unequal in working face,which is main cause of support buckling in long-wall mining stope.