Study on Damage Law of Raw Coal Based on Different Characterization Methods

Abstract

The different damage variables equation based on strain, energy dissipation, acoustic emission (AE), and permeability characteristics under tiered cyclic loading were defined. The damage variables based on different characteristics were compared, analyzed, and found that there are similarities and differences between them. The results show that: (1) the law curve of single cycle damage based on residual deformation and permeability is the same. With the increase of cycle times, it decreases first and then gently increases, increased sharply before the failure. However, the law curve of single cycle damage based on energy dissipation and AE ring count shows that it first increases slowly and the adjacent failure increases rapidly. (2) The cumulative damage evolution law based on residual deformation and permeability show an obvious three-stage pattern; that is, first accelerates, then slows down, and then accelerates again. However, the cumulative damage evolution law based on energy dissipation and AE ring count shows an obvious two-stage pattern, that is, first gently increases, and increased sharply before the failure.