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

Abstract

The strain energy storage index W_ET 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 W_ET 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 W_ET 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 W_ET is extremely close to the ideal and general ESD ratio, which proves that the selecting stress level of W_ET calculation is scientific and reasonable. Furthermore, the general ESD ratio converges to the peak ESD ratio (namely peak strain energy storage index W_ET^P) as stress level increases. Compared with W_ET, W^p_ET not only reflects the ESD ratio of coal materials over the whole pre-peak loading stage, but also exhibits excellent stability. Consequently, W^p_ET is suggested as a new evaluation index of coal burst liability.