Proposing a novel comprehensive evaluation model for the coal burst liability in underground coal mines considering uncertainty factors

Coal burst is a severe hazard that can result in fatalities and damage of facilities in underground coal mines.To address this issue,a robust unascertained combination model is proposed to study the coal burst hazard based on an updated database.Four assessment indexes are used in the model,which are the dynamic failure duration(DT),elastic energy index(WET),impact energy index(KE)and uniaxial compressive strength(RC).Four membership functions,including linear(L),parabolic(P),S and Weibull(W)functions,are proposed to measure the uncertainty level of individual index.The corresponding weights are determined through information entropy(EN),analysis hierarchy process(AHP)and synthetic weights(CW).Simultaneously,the classification criteria,including unascertained cluster(UC)and credible identification principle(CIP),are analyzed.The combination algorithm,consisting of P function,CW and CIP(P-CW-CIP),is selected as the optimal classification model in function of theory analysis and to train the samples.Ultimately,the established ensemble model is further validated through test samples with 100%accuracy.The results reveal that the hybrid model has a great potential in the coal burst hazard evaluation in underground coal mines.

Peak-strength strain energy storage index for evaluating coal burst liability based on the linear energy storage law

The strain energy storage index WET was widely used to evaluate coal burst liability,but the scientific evidence for selecting the unloading stress level interval(around 80%of peak strength)remains lacking,and WET can not reflect the energy storage and dissipation ratio(ESD ratio)of the whole pre-peak stage for coal materials.In this study,these two key problems in WET calculation and application were solved based on the linear energy storage(LES)law.The LES law was defined as the linear relationship between the elastic strain energy and input strain energy for solid material during loading.Using the LES law,the elastic strain energy and dissipated strain energy of at 10 types of coals were calculated precisely,and ideal ESD ratio and general ESD ratio at any stress level will be obtained subsequently.The results also show that WET is extremely close to the ideal and general ESD ratio,which proves that the selecting stress level of WET calculation is scientific and reasonable.Furthermore,the general ESD ratio converges to the peak ESD ratio(namely peak strain energy storage index WET P)as stress level increases.Compared with WET,Wp ET not only reflects the ESD ratio of coal materials over the whole pre-peak loading stage,but also exhibits excellent stability.Consequently,Wp ET is suggested as a new evaluation index of coal burst liability.