Fatigue damage evolution characteristics and time effect analysis of coal rock based on CT three-dimensional reconstruction
摘要
In order to deeply explore the fatigue damage evolution characteristics of coal rock under different creep damage conditions, and reveal the internal relationship between the structural changes of complex pores and fractures in coal rock and its deterioration and instability, based on the indoor test results, the quantitative analysis of three-dimensional reconstruction of coal rock with different creep damage and the fractal analysis of fracture box dimension are carried out to study the structural changes of complex pores and fractures in coal rock in detail. With the help of PFC3D numerical simulation software, coal rock samples with different random pore fracture rates are generated, and the fatigue characteristics of coal rock under different creep damage conditions are simulated. The results show that the size, number and connectivity of pore cracks in coal samples are highly random due to the influence of loading time and individual differences. The crack box dimension of creep damage coal sample increases significantly, and the internal pore crack structure of coal sample becomes more complex, disordered and accompanied by stage characteristics over time. The numerical simulation results of coal rock are close to the failure mode and mechanical properties of indoor samples. The randomly generated pore fracture rate in coal samples has obvious threshold effect on the deterioration and instability of coal samples. Below this threshold, the pore fracture is not completely discrete, and only the deterioration area with high degree of connectivity is formed locally, resulting in obvious local tensile shear failure. Above this threshold, the sample is dispersed into several small units by randomly generated pore cracks, the overall strength of the coal sample is greatly reduced, and the failure mode is overall plastic failure.In the creep test, there are obvious stage characteristics in the expansion of internal cracks and the development of new cracks in coal roc