Damage and fracture law of coal samples with different joint angles and their characterisation by acoustic emission

The application of the acoustic emission (AE) and damage theory to the evaluation of coal rock stability requires a clear comprehension of the influence of joints. The mechanical and AE response characteristics and damage evolution characteristics of samples with different joint angles were analysed through uniaxial compression tests. The results show that the angle between the loading principal stress and joint surface considerably influences the mechanical characteristics of samples and the damage degree characterised by the AE. However, the existing models of AE damage characterisation do not fully reflect the damage characteristics of samples with different loading principal stresses and joint surface angles. In this paper, the improved damage model characterised by the AE count accumulation is proposed. The model has clear physical and mechanical bases and can effectively characterise the damage catastrophe characteristics of the samples with different joint angles. It also has an important application value in coal and rock dynamic disaster monitoring and early warning, damage detection and other projects.