Abstract:
In order to further study the energy evolution and damage failure of coal specimen subjected to step creep loading, the Shimadzu AX-G250 test machine was used to carry out the creep test of coal specimen subjected to step loading. Test results show that the stress level has a significant influence on the creep process of the coal specimen, the creep stress level before the coal specimen failure, with the increase of the creep stress, the duration of the initial deceleration creep phase gradually increases. The energy evolution can be divided into four phases, namely: energy stagnation, steady energy increase, significant energy increase, and energy release phases. With the increase of creep stress level, the ratio of elastic energy to dissipated energy presents a “U”-typed evolution law. The damage equation based on the dissipated energy method shows that the creep damage process of coal specimen subjected to step loading can be divided into the linear increase and non-linear significant increase phases; and the appearance of the latter phase can be used as the precursor of coal specimen creep failure subjected to step loading.