Mechanism Study On The Behavior Of Anchor Bolts By Numerical Tests Simulated With RFPA

As one of the most important and effective methods, bolt reinforcement is used to solve the complex problem in the Rock Engineering. But the status quo of which the theoretical study lags behind the application of anchors will stunt the development of anchoring technology. Therefore, a series of numerical experiments by using a newly developed numerical code, Rock Failure Process Analysis (RFPA), which has been used successfully to simulate the rock failure processes concerning some nonlinear and discontinuous mechanical problems, were carried out to investigate the load-transferring mechanism of rock bolts.In this paper a number of tension tests with single anchor have been performed by orthogonal experimental method to check the influence of 6 main factors on the failure strength of the anchor. And the data from those tests reveal that except increasing the embedment depths of the bars, other methods such as resin bond with high strength, ribbing steel bars and smoothing the hole surface can also be taken into account to increase the anchoring tensile strength and may get better results. Additionally, the anchor system with resin bond and smooth borehole surface will provides more deformation before destroy to avoid the brittle failure suddenly.To investigate how the space between anchors influence the failure strength, numerical tests with group anchors have been carried out. The results show that when the space of anchors is smaller than certain value and the bar and rock bond well, the group effect appears. From the tests, the condition under which the group effect must be considered, and a formula to calculate the failure strength of group anchors were derived. In addition, if the bond between rock and steel bar is too weak, the bond failure occurs even the group anchors are in small space, and the load undertaken by every anchor is much lower than the load of single anchor. In that case the anchor reinforcement will hardly be effective. For avoiding such a case, a formula that the bond strength should fulfill is presented.In practice, the bolt may endure shear force while it is being pulled. The ultimate tensile forces of single anchor under different shear forces were studied by RFPA numerical experimental method. Test processes were observed and can be used to explain why the tensile failure load reduces when the anchor endure shear force at the same time. The experimental results show that the anchor can bear more shear loads when they are inclined to the shear surface than the shear loads when they are upright under the same tensile load. And there is a curvilinear relation between relative shear forces and relative tensile strength. According to the relation above, a formula to calculate the failure loads of anchors under shear forces is presented.