Dynamic damage characteristics of coal and rock under different loading conditions based on CT scanning 3D reconstruction technology

As a complex natural material, the mechanical behavior and damage characteristics of coal and rock have important research value in the fields of mining engineering, underground space development and energy mining. Coal and rock materials have heterogeneous and anisotropic characteristics, so it is difficult to carry out repeated tests and quantitative analysis of internal damage. Therefore, CT scanning and three-dimensional reconstruction technology are used for numerical simulation modeling. At the same time, combined with the corresponding rock mechanics experiments, the auxiliary mechanical parameters are checked, and the dynamic damage characteristics of coal and rock under uniaxial compression and triaxial compression are studied. The industrial CT scanning system was used to scan the raw coal sample, and Otsu method was used to segment the original CT image to extract the fracture and mineral matrix. The three-dimensional space network of the internal cracks and mineral matrix of raw coal samples was constructed by using the three-dimensional reconstruction technology, and imported into the FLAC^3D numerical simulation software for modeling. The fractal geometry method was used to verify the numerical model. After calculation, the maximum error between the fractal dimension of the original CT image and the fractal dimension of the corresponding slice image in the FLAC^3D numerical model was 2.306%, and the numerical model was basically consistent with the CT scan image of raw coal samples; The mechanical parameters in the numerical simulation were assigned by the uniaxial compression, acoustic emission and Brazilian splitting experiments carried out in the laboratory. The mechanical parameters in the numerical simulation were checked by comparing the uniaxial compression stress-strain curve and acoustic emission response characteristics of raw coal specimen and numerical model, and the FLAC^3D numerical model with reliable model and reasonable parameters was obtained. Taking the ratio of plastic element to total element in the numerical model as the damage variable, the change law of coal rock damage variable under uniaxial compression and triaxial compression price adjustment was studied, and the dynamic damage evolution equation of coal rock under uniaxial compression and triaxial compression price adjustment was established.