Numerical simulation of interface mechanical effects of primary coal-rock combination

The interface of primary coal-rock combination is heterogeneous and contains a lot of complex microstructure. In order to solve the complex physical field caused by heterogeneous coal-rock interface transparently, industrial CT was used to scan the specimens of primary coal-rock combination. The three-dimensional model of primary coal-rock mass interface was reconstructed, and the fractal dimension of heterogeneous coal-rock interface was calculated. Based on this, a numerical simulation model of primary coal and rock mass was established, and the stress and damage characteristics of primary coal-rock combination under uniaxial compression were simulated and analyzed. The reliability of the numerical simulation law was verified by the uniaxial compression test results of coal-rock combination. The results show that: the interface of primary coal-rock combination has complex microstructure and fractal characteristics, and the fractal dimension can reflect the macroscopic morphology of interface. Under uniaxial compression, the vertical stress in the primary coal-rock combination exhibits non-uniform distribution. The presence of coal-rock interface induces horizontal compressive stress in the coal body and horizontal tensile stress in the rock, and the horizontal stress near the coal-rock interface presents an arch distribution. The damage of the primary coal-rock combination mainly occurs in the coal, and the damage of the coal body first occurs in the coal far away from the interface and gradually expands to the interface. The higher the fractal dimension of the interface is, the smaller the axial compression is when the initial damage occurs. Due to the existence of compressive stress arch at the coal-rock interface, the strength of the coal-rock combination is higher than that of the coal mass, and the coal mass after failure is arched. The expected research results are of significance for the prevention and control of coal and rock.