Experimental study and numerical simulation of anchoring mechanism of anchored rocklike material with prefabricated fracture

To investigate the anchoring mechanism and its influential factors of the bolt, a series of uniaxial breaking tests is conducted on the specimen with prefabricated fracture anchored with a single row bolt. A concept of the main-control crack (i.e., one or several large cracks controlling the strength weakening and the ultimate failure) is proposed. Under different conditions of anchorage, the main-control crack of specimen have different occurrences. In the effective anchoring zone, there are two types of main-control cracks observed in the fractured specimens, called the horizontal main-control crack and vertical main-control crack. It is found that specimens without rock bolt or with the cracks beyond the effective anchoring zone only have the vertical main-control crack. Acoustic emission and stress monitoring data show that the bolt can delay the initiation of the main-control cracks and improve the strength of the fractured specimens. Additionally, the stress intensity factors on the tip of cracks under different anchoring conditions are calculated using ANSYS software. Then the relationship among the anchoring spacing, anchoring angle and the stress intensity factor is obtained. The coalescence modes of main-control cracks are also simulated under different anchoring spacings by using FLAC(3D) software, and numerical results agree well with the experimental results.