Meso-mechanism of rock failure influenced by bolt anchorage under uniaxial compression loading

As an important support method, the bolt anchoring system is widely used to control the dynamic disasters of deep brittle surrounding rock, but deep rock engineering practices have been beset by the failure of brittle rock with bolt support because the researches on anchorage theories still lag behind. Based on the failure characteristics of brittle surrounding rock with bolt support in practical engineering, such as shallow surface damage and local damage, uniaxial compression fractures of intact brittle specimens influenced by bolts with different diameters are studied by means of laboratory similarity model tests. The test results show that the relationship between bolt diameters and the promotion of the elastic modulus and strength of brittle rock should be matched optimally, and only increasing the bolt diameter can not control ideally the brittle surrounding rock. Also, bolt anchorage can change the uniaxial compression failure mode of brittle specimens, macroscopically, the splitting failure can be transformed into shear one, and the extent of shear failure is determined by the bolt diameters as well. From the angle of meso-scale mechanism, the crack propagation model with two main internal cracks is established to analyze the fracture change of anchored specimens, and its main factor can be attributed to the inhibition effect on the propagation of internal cracks influenced by the bolt anchorage which decreases the length ratio η of the wing crack to the main crack. According to the calculated results of most-easily-cracking angle ζ, the long wing crack wing extends towards the loading direction which mainly induces its splitting failure, conversely, the short wing crack deviates from the loading direction which mainly causes its shear failure. The fracture mechanism of anchored brittle specimens can be revealed preferably in the view of meso-scale.