# Structural Evaluation of Cable Bolts under Static Loading
## 6 Limitations of the Study  
The model simulated the effects of a rock burst impacting a cable bolt. Whilst it yielded valid results, the model and testing methods could be improved. The primary limitation of the study is the simplification of the model itself. The configuration and embedment of the cable bolt are critical parts of the cable bolt design. As seen in Figure 2, there are various geometrical arrangements for the bolt. The purpose of this is to provide various gripping strengths and additional tensile capacities. By reducing the bolts to a simple cylindrical cable bolt and manually applying slip conditions, this does not provide an accurate depiction of the effect of the cable bolt design. To improve the model, careful construction of the cable bolt design should be conducted. Interwoven mesh bolts contain the intentional design to increase tensile and shearing capacities by increasing the number of contact surfaces. The purpose of the bulbed cable bolt is to allow energy to be suddenly dissipated if stresses reach a capacity. This effectively increases the overall energy dissipation of the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Maximum Shear Load (kN)**} \\ \hline
**Bolt Diameter** & \(f_{y}\) = 500 Mpa & \(f_{y}\) = 565 Mpa & \(f_{y}\) = 633 Mpa & \(f_{y}\) = 847 Mpa & \(f_{y}\) = 922 Mpa & \(f_{y}\) = 1382 Mpa \\ \hline
**18** & 129.0 & 136.4 & 189.0 & 185.0 & 211.3 & 339.3 \\
**20** & 186.4 & 197.5 & 269.4 & 270.5 & 302.0 & 492.5 \\
**23** & 254.8 & 272.3 & 369.2 & 364.5 & 409.8 & 705.7 \\
**25** & 305.1 & 325.8 & 443.1 & 441.3 & 497.8 & 848.0 \\
**28** & 394.8 & 423.0 & 582.6 & 575.4 & 647.0 & 1084.5 \\
**31** & 498.1 & 535.5 & 721.3 & 716.6 & 818.4 & 1301.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 11: Maximum static shear load of bolts. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{6}{c}{**Maximum Displacement at Failure (mm)**} \\ \hline
**Bolt Diameter** & \(f_{y}\) = 500 Mpa & \(f_{y}\) = 565 Mpa & \(f_{y}\) = 633 Mpa & \(f_{y}\) = 847 Mpa & \(f_{y}\) = 922 Mpa & \(f_{y}\) = 1382 Mpa \\ \hline
**18** & 36.2 & 36.9 & 45.1 & 41.6  
bolt, which cannot be replicated using this simplification. Ultimately, these design factors are significant factors that contribute to the bolt capacity that are omitted from testing. The calibration of the model was not ideal as it was not precisely calibrated against an identical test. The model it was calibrated against included the contact properties between the concrete blocks. This condition was omitted and instead included a 50 mm gap to effectively reduce the number of contact points. Without proper definition of contact properties over a large contact surface area, the model is likely to experience convergence issues, resulting in a greater computational time and potentially invalid results. [PERSON] et al. (2021) [PERSON] et al. (2021) partially attributes the dissipation of shear forces to overcome frictional forces. By using the Mohr-Coulomb and Fourier series relationship, he estimated that approximately 30% of the shear force was redirected to overcome the frictional forces of the contact surfaces. Cable bolts need to be correctly anchored into the rock mass to allow for the induced axial tension load from rock deformation to bind the rock mass together [PERSON] et al. (2021). This is achieved by three techniques, namely grouting using resin or cement, friction and a mechanical device. They all share the same purpose of increasing the contact surface area between the cable bolt and the rock surface to ultimately provide a binding action between the two materials. The anchoring process is unique to the bolt and manufacturer. This model does not account for any grouting, as it was assumed that this connection would be fully frictional. By assuming the bolt to be perfectly cylindrical and the box to have a perfectly rounded hole, the bolt will be in full contact with the box. This is unrealistic as it bypasses the need for the grout.