Influence of Stresses and Displacements in Roof Rocks on Roof Fracture in Top Coal Caving
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Influence of Stresses and Displacements in Roof Rocks on Roof Fracture in Top Coal Caving V. E. Mirenkov Chinakal Institute of Mining, Siberian Branch, Russian Academy of Sciences, Novosibirsk, 630091 Russia e-mail: [email protected] Received March 5, 2020 Revised April 9, 2020 Accepted April 10, 2020 Abstract—The process of roof caving at face during its advance is impossible to describe by static and kinematic solutions. It is necessary to take into account unsymmetry of deformation due to the dynamic component of the roof caving process. To that end, it is required to undertake experimental and theoretical studies into the unsymmetrical displacement distribution. It seems to be possible to obtain additional information on deformation and caving of roof rocks from the elastic solution. The main factors to ensure correct formulation of problems are the statics, kinematics and dynamics of rock mass deformation, and the proposed description of the inelasticity zone in the host rocks–mineable seam system. Keywords: Longwall, seam, difficult top coal, displacements, statics, kinematics, dynamics. DOI: 10.1134/S1062739120026650
INTRODUCTION
This study develops the approach connected with the static, kinematic and dynamic aspects of rock mass deformation in the course of mineral mining as it eliminates ill-posed formulations of problems in geomechanics while such formulations are numerous [1]. Ill-posedness ensues from disagreement between the mathematical and physical problems which are used. The kinematic aspects allows taking into account the overlying rock weight [2], which is yet neglected in the analytical solutions, reducing the static calculation to formulation of an additional problem and avoiding ill-posed formulations of a Cauchy problem [3–13]. According to the general theory of equations of mathematical physics, the Cauchy problems with computational domains with a point at infinity belong to a special class. In particular, the problems for a half-plane and a plane with holes, or for a space and a half-space with cavities. As powered roof support is advanced, roof rocks come into shock interaction with the support and mineral seam, which leads to accumulation of damages in rock mass. The mineral seam is the most subjected to breakage, and its face zone deforms nonlinearly. It is required to delineate the nonlinear deformation zone and to know the nature of compression of the seam by enclosing rocks as this compression is elastic beyond the nonlinear deformation zone. In this case, it is possible to calculate elastic displacements of the roof, i.e. to integrate the static and dynamic aspects, and then to add them with the kinematic displacements. The proposed model is based on the
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