Micro Strain Localization and Failure Behavior of Coal Gangue Interbedded Sediment

The presence of coal gangue has a significant impact on the mechanical behavior of the coal seam, which in turn seriously affects the stability of the well wall. In this study, the influence of coal gangue on the micromechanical behavior of coal seam core is studied by taking the coal rock of typical deep coalbed methane reservoirs in China as the research object. The results show that the compressive strength of coal gangue is 41 MPa higher than that of no. 8 coal, the elastic phase of the stress–strain response of coal samples from coal gangue beds is longer, and the strain of coal samples is larger when they are damaged, which indicates that the coal gangue has higher stiffness and greater hardness. In addition, digital volume correlation (DVC) was applied to calculate the equivalent strain and strain components of no. 8 coal and gangue, and it was found that the strain concentration of no. 8 coal appeared mostly in the cracks of coal samples and the junction of coal matrix and gangue, while the strain high-value area of gangue was distributed in the form of speckles or blocks in the coal samples.