Study on energy dissipation and damage evolution of bump proneness coal under cyclic loadings

In order to study the energy dissipation features and damage evolution process of the bump proneness coal under the condition of the multi cyclic loadin gs, a multi cyclic loading experiment was conducted in a lab on the coal samples from a coal mine in Shaanxi.The experiment study showed that under the multi grade s tress cycle, the dissipated energy of coal sample would be rapidly decreased firstly and then would be slowly increased.When the cycle upper stress reached at the 6 3% failure load, the dissipated energy would start the serious increased.But the energy dissipation rate would be firstly and rapidly decreased and then would be steadil y stabillized.The elastic modulus of coal sample at the unloading and loading stage would be all in an increasing tendency.At the loading stage, the elastic modulus woul d be firstly increased rapidly and then would be slowly increased. But the variation of elastic modulus would be stable at the unloading stage. The damage variation of sa mple in a circulated loading with an accumulated dissipated energy definition was applied to establish the damage evolution equation of coal sample and each paramet er was measured with the experiment and numerical calculation.The theoretical and experiment study showed that the damage evolution equation of the bump pronene ss coal established based on the energy dissipation analysis could well reflect the damage evolution process of coal sample.