Investigation on Pore-fracture of Coal and Its Influence Mechanism on Uniaxial Compression Failure Behavior

Pore-fracture is an important component of coal, affecting the uniaxial compression failure behavior. However, it is difficult to effectively characterize the influence mechanism because of the complexity and randomness of components in coal. In this paper, scanning electron microscope (SEM), computed tomography (CT), indentation hardness and uniaxial compression tests are conducted for specimens with high, medium and no bursting proneness to investigate it. The results indicate that distribution of three components (matrix, minal and pore-fracture) in specimens are extremely different, which is the embodiment of tectonic structure activity and geological condition of mineralization. The levels of bursting proneness of coal, the tectonic structure features, tectonic structure activities and external functions are related. 3-D reconstruction on the basis of CT images can visualize internal complex structure of specimens. The numerical simulation results demonstrate that distribution of pore-fracture, mechanical properties of matrix and minal are significant inducement of specimen's failure difference in the identical loading mode. Main failure mode of specimens with high, medium and no bursting proneness are different, which proves that main failure mode of specimen correlates with its mechanical properties. The mechanical failure behavior of specimen under uniaxial compression is influenced by loading mode, mechanical properties of matrix and minal, pore-fracture feature and other considerations. The loading mode is extrinsic cause of mechanical failure behavior of specimens, also an inducing factor and could be intervened. Furthermore, mechanical properties of matrix and minal determine bearing capacity and ultimate failure mode of specimens. Primary pore-fracture seriously affects extension process and extension mode of secondary pore-fracture, and the internal damage development of specimens. Notably, coal composed by the convergence of matrix, minal and pore-fracture, all these are internal cause of mechanical failure behavior of specimens, which belong to basic factors and hard to be intervened.