Study on load transmission characteristics of overburden rock above coal mining face in thin bedrock of super thick unconsolidated stratum

Based on the characteristics of mine water inrush and sand inrush and the powered support jammed accident occurred in a coal mining face in thick unc onsolidated stratum and thin bedrock of partial mining area in North China, in order to provide references to estimate failure “two zones"height in the overburden rock b y mining operations, to predict and overcast the mine water disaster and to set up powered support selection, a key strata theory was applied to establish a load transm ission mechanics model of hard rock complicated breaking overburden rock strata and to infer load transmission coefficients of complex hard rock and overburden rock strata. According to geological characteristics in the study area, a geological mechanics model was established. A numerical analysis was applied to study load transmi ssion effect of mining overburden rock in coal mining face in thin bedrock and overburden rock failure characteristics. The study results showed that load transmission C oefficients of top hard rock and overburden rock strata were 0.24 ~ 0.30 when the hard rock above coal mining face in thin bedrock of thick unconsolidated stratum was complex breaking. When the overburden rock above seam was failure by mining operation, the horizontal section would be an"O-X"type breaking. A caving and mining r atio of overburden rock failure above coal mining face was 3.85 and the fracture and mining ratio was 12. A displacement angle of rock stratum was about 70°. The mini ng fractures at two ends of coal mining face would be major channels of mine water inrush and mine sand inrush.