Author(s)

P. P. Prochazka

Abstract

In several of the author’s previous papers the problem of bumps occurrence has been solved by distinct element methods, namely by free hexagon method. The latter method proved its significance in description of the most probable nucleation of cracks, which at the moment of bumps create the contact surface of the moving part of the coal seam. The movement of particles is also described in a very good manner. In this paper another approach is used. Starting with the aim of describing whether the bumps occur or not, or under which condition, the continuum of both rock seam and the overburden (rock) is considered. The decision whether the bumps are triggered can then be derived from conditions at different points of the coal seam. For the solution, finite element method is used and elastic behavior (more precisely brittle material) of the coal seam and plastic behavior of the rock are assumed. Keywords: bumps in deep mines, mechanical behavior of rock, slip conditions. 1 Introduction Bumps or rock bursts is a phenomenon, which occurs during mining in deep mines. This phenomenon appears during longwall mining, for example, and mostly it is qualified as a sudden release of energy concentrated at the side face of a shaft. This extreme concentration can be caused by material changes in the overburden rock massif, of distant local disturbances, due to creation of cracks, emission of gas, human activities in the neighborhood of the site of mining, etc. In any case, it is necessary not to forget the fact that along the upper part of the shaft where the ceiling and the rock are in contact, a tip of a crack (notch) causes a natural accumulation of energy. From classical theories based on elastic solution such a point is classified as a mass point of singularities and even

Keywords

bumps in deep mines, mechanical behavior of rock, slip conditions.