An analytical approach to study the reinforcement performance of rock anchors

Rock anchors are widely used in rock reinforcement in civil engineering. However, little analytical research has been performed to investigate the anchoring performance of rock anchors when the grout and rock are simultaneously considered. This manuscript proposed an innovative mechanical model for rock anchors when grout flutes and rocks are considered simultaneously. Grout flutes and rocks were combined together to constitute the surrounding system. Then, the equivalent elastic modulus (EM) concept was proposed to simulate the surrounding system. A non-liner three-stage law was incorporated into the rock anchor reinforcement to deduce the loading performance of rock anchors. The loading process of rock anchors was divided into four stages. All input parameters can be obtained and calibrated based on the experimental tension scenario. The accuracy of this mechanical model was confirmed with independent experimental tension cases. An advantage of this mechanical model is that it can consider grout flutes and rocks simultaneously. The other advantage is that it overcomes the snapback phenomenon which occurs in previous modelling. The EM ratio between grout flutes and rocks has a significant impact on the anchoring performance of rock anchors. The larger the EM ratio, the better the anchoring performance of rock anchors. Compared with the largest load, the EM ratio has more apparent impact on the stiffness of the rock anchor reinforcement. Additionally, with the cross-section area of rocks increasing, the anchoring load of rock anchors increases. However, there is a certain limit. When the influencing circle diameter of rocks is beyond ten times of the borehole diameter, further increasing the cross-section area of rocks has marginal impact on the anchoring performance of rock anchors.