Crack initiation and propagation at crack tips of prefabricated flawed sandstone under uniaxial compression

In order to explore the crack initiation and propagation law of fractured rock, uniaxial compression test and DIC digital speckle test were carried out on prefabricated crack specimens with different dip angles, and high-definition camera was used to collect images synchronously. The strength characteristics, crack initiation characteristics and crack propagation law of specimens with different prefabricated crack dip angles were obtained. The results show that the stress-strain curves of prefabricated crack specimens with different dip angles show similar variation rules. The law of crack initiation and crack propagation has a great correlation with the prefabricated crack and its dip angle. The crack initiation stress first increases, then decreases, and finally increases with increasing prefabricated crack inclination angle. Then, a stress intensity factor model with prefabricated cracks is proposed, and the theoretical results are compared with the experimental results. The model can be effectively applied to the determination of crack initiation angle of prefabricated crack rock with different dip angles. The research results can provide some reference for underground engineering construction and geological disaster prediction.