<正>Time dependent(dynamical equilibrium) free hexagon DEM is applied to geomechanical problem,namely to bumps occurrence in deep mines.The time factor is involved in natural way into the model of discrete elements created by the boundary element method.It seems that not too many papers are published on this topic,even in the case of static description of the phenomenon.One can verify this assertion on Internet at special pages of providers of professional technical and mathematical publications.After discussion with a Russian expert it appeared that large publications on this topic are written in Russian and try to explain the course of preparation in the coal and surrounding rock to conditions,when the bumps occur.This paper is focused on exploitation of observation of Russian scientists in connection with modern numerical methods. Two of the most important elements of the bumps occurrence are:the velocity of excavation and the amount and pressure of gas accumulated inside vertical cracks(or inclined cracks) in coal seams,which behaves purely brittle and tensile strength are violated.In deep mines the way of depositing packs and its mechanical properties are also very important.Their mutual coupling with the plastic stiff sides created during the long-wall mining can principally influence the safety against bumps.For correct understanding the behavior of the rock aggregate(coal seam vs.overburden) nucleation of cracks finally leading to bumps has to be treated as time depended,while so far it was observed only from static equilibrium. Contact problems of free hexagons and other problems of that kind leading to bumps occurrence in deep mines have been solved in many papers of the author for static case.The new formulation introduced here is submitted in terms of penalty,which if high enough(bond effect of adjacent elements) suppresses the not only debond of particles but also the influence of time.Involving the interface properties with lumped inertia mass of the elements,complex nucleation can be studied and improve the information on possible rock bursts.
Discrete element method;;boundary element method;;dynamical equilibrium;;rock bumps;;small deformation theory
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