Research on dynamic evolution of 3D fracture structure of loaded coal body based on CT visualization

In order to study the dynamic evolution and morphological characteristics of fractures in loaded coal, the CT scanning system of the loaded coal-rock is used as an experimental platform to investigate the process of deformation and failure of coal samples under uniaxial and triaxial stress loading conditions.Micro-CT scanning test, the CT scan information and stress-strain curve of the three-dimensional fracture structure which can reflect the whole process of the instability of the loaded coal sample are obtained.The VG Studio MAX image analysis software is used to reconstruct the CT scan data.According to the numerical coal core for the precise crack extraction and digital qualitative and quantitative characterization of fracture morphology, the basic changes of coal fracture development under uniaxial and triaxial loading conditions are compared and analyzed.The results show that the industrial CT is an effective mean to study the internal evolution process of cracked coal and rock.The relationship between fracture volume and fracture rate with stress is a direct reflection of the dynamic evolution process of coal-bearing fissures.The fracture volume and the fracture rate show a slow decrease-a slow increase-a sharp increase-a slowing growth rate during the change of stress.The internal fracture evolution of the coal body under the loaded conditions is experienced six stages including initial compaction, elastic deformation, new crack growth, new crack growth, fracture expansion and residual deformation, and the failure mode is shear failure.The yield strength and fracture evolution process of coal samples under triaxial loading and uniaxial loading and the fracture morphology after failure are significantly different, indicating that confining pressure is an important factor affecting the failure process of loaded coal.Industrial CT scan images show that the crack growth is preferentially initiated with the increase of stress load along the contact surface of the mineral and coal matrix.The research results provide a reference for the rational and safe mining of coal and underground support.