Analysis on Relation of Immediate Roof Caving-mining Ratio and Roof Toughness with Ground Behaviors in Fully Mechanized Caving Face

In this paper,analysis was made on the roof structure and lithological properties of the fully mechanized caving face in No. 6 coal seam in Suancigou Coal Mine and two concepts of the caving-mining ratio and the roof toughness were put forward in order to explore the causes of the very strong strata behaviors in this face. Analysis was also carried out on the relation of the caving-mining ratio and the roof toughness with the strata behaviors through the theoretical analysis and calculation as well as the field measurement. The results showed that under the condition of small caving-mining ratio and strong roof toughness,the strata behaviors in the fully mechanized caving face presented the basic features of strong or very strong pressure,the roof was very difficult to control,this was the main factor causing the strong strata behaviors in this fully mechanized caving face of this mine.