Deformed State of the Coal Seam in the Marginal Zone and the Condition of its Destruction during Mining by a Stope Working

The fields of deformations and displacements of the marginal zone of the coal seam are determined on the basis of the associated law of plastic flow, in which the stress components are constructed within the framework of the previously developed model of the geomechanical state of the rock mass containing the coal seam and the workings passed through it. In this model, the stresses in the limiting zone of the seam are determined by the methods of mechanics of the bulk medium developed by the soviet scientist V.V. Sokolovsky. The condition for the destruction of the part of the marginal zone of the coal seam, which, according to the Coulomb-Mohr criterion, passed into the limit state (without hardening), that corresponds to the idealized Prandtl diagram, is that it exceeds the limiting indicator of the intensity of plastic deformations corresponding to the deformations of the coal sample during its uniaxial destruction by compression. This indicator is determined by the results of laboratory experiments with coal samples, or on the basis of available reference information on the mechanical characteristics of coal seams. Destruction of the part of the seam may be accompanied by such a dynamic phenomenon as a rock burst. Seam deformation in the extremely stressed zone is accompanied not only by a decrease in its thickness, but also by the movement of its edge into the goaf. With a significant size of the mined-out space, these displacements (bulging) can extend to several tens of centimeters.