Fully grouted cable bolts are playing a significant role in keeping the stability of underground excavations and surface slopes. To better understand the load transfer of cable bolts, a parametric study was conducted based on an analytical model. The influence of parameters including the bond strength, the residual shear strength, the shear slippage where bond strength occurred and the shear slippage where residual shear strength occurred on the cable bolt performance was studied. The results show that the bond strength played a significant role in determining the maximum pull-out load of cable bolts. While the residual shear strength, the shear slippage where bond strength occurred and the shear slippage where residual shear strength occurred played marginal effect in determining the maximum pull-out load of cable bolts. Nevertheless, all those four parameters had an apparent effect in determining the shear stress distribution along the bolt/grout interface when the peak load occurred.
Cable bolt are flexible tendons composed of multi steel wires. They were initially introduced into the mining industry in the 1960s. After that, it saw a rapid development of cable bolt application in mining and civil industry. Numerous in-situ tests proved that cable bolts are playing a significant role in keeping the stability of underground excavations (Meng et al., 2015; Wang et al., 2015).
After the borehole is drilled, the cable bolt can be point anchored or fully grouted with the bonding agent in the borehole. Previous research indicated that the polyester resin or cement-based grout can be used as the bonding agent (Thompson et al., 2012). Additionally, when fully grouted cable bolts are used, the cement-based grout is usually selected as the bonding agent because of its superior flow ability. This paper deals with the fully grouted cable bolt.
In the in-situ case, the fully grouted cable bolt is loaded because of the rock mass movement. Then, shear stress is induced along the bolt/grout interface and the grout/rock interface. However, since the contact area of the bolt/grout interface is always smaller than the grout/rock interface, the shear stress along the bolt/grout interface is larger than that along the grout/rock interface. When the shear stress is larger than the bond strength of the bolt/grout interface, bond failure occurs along the bolt/grout interface, which has been proved by numerous experiments (Chen et al., 2017; Thenevin et al., 2017; Li et al., 2018).