## 4 Discussion
### Angle of Triangular Sawteeth  
Figure 11 shows a box-and-whisker plot of the dynamic peak stress at various angles, \(\alpha\), for the specimen with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\). For the specimen with \(\beta=39^{\circ}\) (Figure 11a), the middle 50% of the box that represents the dynamic peak stress due to crushing failure, the dynamic peak stress is typically higher than those caused by slide failure and fracture failure, especially for \(\alpha=0^{\circ},3^{\circ}\), and \(6^{\circ}\), revealing that the dynamic peak stress of the specimen dominated by crushing failure differs from those by other failure types. The dynamic peak stress in the middle part of the box that is associated with crushing failure of the specimens with \(\beta=45^{\circ}\) and \(51^{\circ}\) partially overlaps those in boxes associated with other failure types (Figure 11b,c). The differences in the dynamic peak stresses that are dominated by various failure types are not great. However, for a particular \(\alpha\) angle, the mean dynamic peak stress of a specimen due to slide failure is lowest, to fracture failure is second lowest, and to crushing failure is highest.  
Figure 12 shows the box-and-whisker plot of the ratio of dynamic peak stress to loading rate (DSLR) at various \(\alpha\) angles for the specimen with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\). Typical DSLR values are in the range 0.02-0.08. In contrast to Figure 11, for the specimens that have the same \(\alpha\) angle but exhibit different failure types, the dynamic peak stress in the middle 50% of the box that represents dynamic peak stress due to crushing failure is typically lower than those due to slide failure and fracture failure. These results indicate that increasing the loading rate increases the dynamic peak stress of a jointed specimen upon slide failure and fracture failure. The mean DSLR value for a specimen that fails by fracture is typically lower than that of specimen that undergoes slide failure and has the  
same angle, \(\alpha\). However, the middle parts of their corresponding boxes have similar DSLR values, indicating variations in the relationship between DSLR value and loading rate.  
Figure 13 plots the change in the DSLR with the \(\alpha\) angle for the specimen with \(\beta=39^{\circ}\). When slide failure or fracture failure occurs, the DSLR increases linearly with \(\alpha\), with coefficients of determination,  
Figure 11: Box-and-whisker plot of dynamic peak stress at various angles, \(\alpha\), for specimens with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\)(**a–c**).  
Figure 12: Box-and-whisker plot of ratio of dynamic peak stress to loading rate (DSLR) at various angles, \(\alpha\), for specimens with \(\beta=39^{\circ}\), \(45^{\circ}\), and \(51^{\circ}\)(**a–c**).  
\(R^{2}\), of 0.688 and 0.886 respectively, revealing medium to high correlations. However, when crushing failure happens, the coefficient of determination for the linear regression between the DSLR and \(\alpha\) is very low, indicating that the angle, \(\alpha\), is not a significant factor under such a condition. Similar results are obtained for specimens with \(\beta\) = 45\({}^{\circ}\) and 51\({}^{\circ}\). Increasing \(\alpha\) increases the DSLR of the jointed specimen, but this effect is further influenced by the \(\beta\) angle of the specimen and its associated failure type.