7 CONCLUSIONS
In this paper, similar simulation materials are used for prefabricating specimens with holes and anchors, and laboratory uniaxial compression tests are carried out. The strength, deformation characteristics, and the laws of crack propagation are studied by using the CT scan, and the coupled stress-damage simulation tests are carried out by using the 3DEC numerical simulation method. The damage evolution process of the specimens with bedding and holes under the action of support structures is discussed.
The support structures can improve the uniaxial compressive strength of the specimens, but different support structures exhibit different degrees of supporting effects on the strength of the specimens. The bolts can significantly improve the strength of the specimens, but the supporting effects of concrete and steel arches are not evident. With different bedding angles, the support structures also show different strength enhancement effects on the specimens. The support structures demonstrate a better effect on improving the strength of the surrounding rock of the specimens with a bedding angle of 90° than the specimens with a bedding angle of 0°.
Concrete and steel arches can induce support pressure on the tunnels, effectively prevent the holes from peeling, spalling off and other damages and help maintain the integrity of the holes. The existence of bedding surfaces can affect the failure process of the rock mass and the distribution of the secondary cracks, but it cannot affect the final failure mode.
The analytical formulas related to the stress and the displacement of the surrounding rock in the anchored area and the non-anchored area under the action of supporting structures are discussed herein. Based on the test results, it is concluded that the bolts primarily realize the anchoring effect by changing the stress state of the surrounding rock in the anchoring area and by improving the mechanical parameters of the surrounding rock. The anchoring area demonstrates the functions of weakening, arresting, and changing the propagation path of cracks, which thus improves the bearing capacity of the surrounding rock.