Experimental study on influence of lithology on directional propagation law of type-I cracks

To study the influence of lithology on the directional propagation law of rock type-I cracks, a simple crack directional propagation device was used to conduct loading tests on three rock types. The acoustic emission (AE) and displacement field characteristics during crack directional propagation were analyzed, and the propagation mechanism of type-I cracks was discussed. The results indicate that the post-peak load curve of white sandstone showed a gradually decreasing trend, while marble and grey sandstone showed a steep decreasing trend. The AE evolution during crack propagation can be divided into four stages: quiet, slowly increasing, booming, and decreasing. For white sandstone, the duration of the first three stages was short, and the decreasing stage was long. However, the opposite trend was observed for the other types. The crack propagation process includes three stages based on the evolution law of the horizontal displacement field: elastic deformation, microcrack nucleation and coalescence, and crack initiation and propagation. The white sandstone enters the microcrack nucleation and coalescence stage earlier than marble and grey sandstone. The length of the fracture process zone of white sandstone was larger than those of marble and grey sandstone; thus, its crack directional propagation rate and stability were lower.

Automated summary

A crack directional propagation device was used to conduct loading tests on three rock types in order to study the influence of lithology on the directional propagation law of rock type-I cracks. The acoustic emission (AE) and displacement field characteristics during crack directional propagation were analyzed, and the propagation mechanism of type-I cracks was discussed. The results showed different behaviors in load curves and AE evolution for different rock types. The length of the fracture process zone and the stability of crack directional propagation were found to be influenced by the lithology.