# Structural Evaluation of Cable Bolts under Static Loading
## 5 Discussion  
The static model investigated the effects of varying the bolt diameter and bolt strengths. The results show a net positive correlation between bolt energy capacity absorbed. The deflection patterns when varying the bolt diameters and yield strengths agree with the results obtained by [PERSON] et al. (2021) [13] and [PERSON] et al. (2017) [2].  
Figure 12: Comparison of 18 mm bolt (**top**) 23 mm bolt (**bottom**).  
Due to the use of quasi-static testing and the application of mass scaling throughout the entire model, this renders the entire model time independent. Therefore, only time-independent analyses can be accurately extracted from the test. Energy absorption cannot be obtained from the analysis. An initial shear failure can be seen in the initial phase of the test, where a sudden spike in force is followed by a sudden reduction. Here, the cable bolt experiences a shear failure. The bolt continues to resist deformation due to the combined shear and bending actions resisting the load. This pattern can be seen when both varying the bolt diameter and the yield strength. This behaviour is most pronounced when the yield strength is 1382 MPa. There are three primary stages of bolt stresses: initial shear failure, combination of shear and bending failure and complete failure (see Figure 13).  
It was expected that the peak force and displacement would be observed when the yield strength and bolt diameter were at a maximum. Interestingly, when yield strength was increased from 633 Mpa to 847 Mpa, little to no change was seen. This was likely due to an input error, and thus is considered an outlier. The displacement of the bolt at failure increases, but the overall max. energy capacity does not make a significant increase despite increasing the yield strength by 34%. Whilst the data obtained from the FEA illustrate a gradual failure of the cable bolt, this is due to inaccuracies with modelling. Therefore, the bolt will be considered completely failed once the bolt reaches a peak force. A summary  
Figure 13: Three stages of bolt failure under static loading conditions.  
of the maximum shear load corresponding to its respective shear strengths is tabulated below in Table 11. Similarly, Table 12 compares the maximum displacement at failure for the respective bolt diameters and yield strengths.  
There is a positive correlation between the yield strength and bolt diameter and the maximum force and displacement. This result is expected, as by increasing the yield strength, the bolt increases the amount of force required to induce plastic deformation. Similarly, this principle also applies to deformation. It is expected that as the bolt diameter increases, the second of moment of area also increases. Furthermore, as deflection is inversely proportional to the second moment of area, the greater the diameter, the lesser the deflection. As area and steel strength are directly proportional to the shear capacity, by increasing the overall area and shear strength, the overall shear capacity increases. The results obtained from the analysis agree with current literature, whereby increasing the bolt size and yield strength results in a greater shear capacity at a larger displacement. The results obtained from the static test align with the current literature and experimental data modelling the double shear test [2; 5].