Study on load transmission mechanism and limit equilibrium zone of coal-wall in extraction opening.

Based on the mechanical model of the coal-wall in extraction opening under high bearing pressure, this paper analyzed the basic distribution of the stress on the interfaces between the coal and rock and the axial force of coal. It first mechanically derivated the total horizontal displacement of the coal and established a new theoretical width formulas about the limit equilibrium zone in sidewalls. On this basis, discussed the main factors of the width without failure zone. The analysis results show that the stress and level pressure of the coal in the limit equilibrium zone distributes at the pattern of hyperbolic function. The vertical stress of the sidewall coal changes by the roadway height and mechanical parameters on the interfaces between the coal and rock. The horizontal displacement increases with the lateral pressure coefficient and peak stress of the elastic-plastic interface and the width of the limit equilibrium zone, while inversely proportional to the average elastic modulus of the coal. The width of the limit equilibrium zone depends on the external factors such as extraction opening depth, the average density of the overburden, the strength parameters of the interfaces between the coal and rock, stress concentration factor, lateral pressure coefficient, extraction opening height as well as composite elastic modulus of the coal. It increases with the addition of the extraction opening depth and extraction opening height and decreases with the addition of the internal friction angle and cohesion interfaces between the coal and rock. Finally, the rationality of these results were verified by an engineering example. [ABSTRACT FROM AUTHOR]