HEREDITARY PROBLEMS IN LONG-WALL MINING BY FREE HEXAGONS
Abstract
In deep mines, the way of excavation, depositing packs, and the mechanical properties as well as the velocity of mining belong to the most decisive phenomena for the threat of bumps. In this paper, time-dependent hereditary creep problem in terms of free hexagon distinct element method (DEM) is formulated and solved for assessment of bumps occurrence in deep mines. The time factor as an impact of the velocity of mining is involved here in a natural way in the model of discrete elements. Inside of these elements, the material behavior is described by the boundary element method. Mutual coupling of the velocity and the way of deposition of packs can principally influence the safety against bumps. For the correct understanding, the behavior of the rock aggregate (coal seam and the overburden) and the nucleation of cracks finally leading to the bumps have to be treated as time depended and creep and viscoplasticity in the overburden should be considered. In the coal seam, brittle material is adopted. According to the new experiments on scale models and results from accessible literature those effects will be involved into the formulations.
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