Abstract
In order to study the mechanism and characteristics of the first breaking of the roof in thick coal seams with high dip angles, a mechanical model of elastic thin plate with four clamped edges of the roof was established, and the expressions of the deflection and stress of the roof were obtained by the energy method. The influence of the change in seam dip angle on the first breaking distance of the roof was presented. Based on the stress solution, the roof breaking criterion was proposed, and the breaking distance of the roof was calculated. Combined with numerical simulation, the stress distribution characteristics of the upper and lower surfaces of the stope roof were analyzed. The results show that the first breaking distance of the roof is inversely proportional to the seam dip angle. Broken morphology of roof in high dip seam is different from the “O-X” morphology of horizontal roof. The roof breaking order of the seam with high dip angle is middle-middle upper-middle lower-upper-lower. These research results have certain theoretical guiding significance for the study of the first breaking mechanism of the main roof of highly inclined working face of coal seams.
Highlights
In order to study the mechanism and characteristics of the first breaking of the roof in thick coal seams with high dip angles, a mechanical model of elastic thin plate with four clamped edges of the roof was established, and the expressions of the deflection and stress of the roof were obtained by the energy method. e influence of the change in seam dip angle on the first breaking distance of the roof was presented
The stress distribution characteristics of the upper and lower surfaces of the stope roof were analyzed. e results show that the first breaking distance of the roof is inversely proportional to the seam dip angle
Broken morphology of roof in high dip seam is different from the “O-X” morphology of horizontal roof. e roof breaking order of the seam with high dip angle is middle-middle upper-middle lower-upper-lower. ese research results have certain theoretical guiding significance for the study of the first breaking mechanism of the main roof of highly inclined working face of coal seams
Summary
Received 7 June 2020; Revised 28 August 2020; Accepted 6 September 2020; Published 16 September 2020. In order to study the mechanism and characteristics of the first breaking of the roof in thick coal seams with high dip angles, a mechanical model of elastic thin plate with four clamped edges of the roof was established, and the expressions of the deflection and stress of the roof were obtained by the energy method. For this working face, a is the advancing distance, b is the inclination length, and α is the inclination angle. Substituting equation (5) into the formula giving the relationship between the deflection and the stress of the rectangular thin plate in elastic mechanics, three stress components of the main roof of the high dip seam are obtained as follows: 4π2Ezq cos α ∞ ∞ m2/a2cos(2πmx/a)(1 − cos 2πny/b) + μn2/b2cos(2πny/b)(1 − cos 2πmx/a).
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