## 5 Conclusions  
In this study, intact rock-like specimens and specimens with closely contacted regular asperities at various angles are prepared for SHPB testing. The effects of loading rate, angle of base plane, and asperity on the dynamic peak stress/strength of the specimens are examined. The following conclusions are drawn.  
1. The appearance of a joint makes the outcomes for a specimen in an SHPB test more diverse. The failures of an intact specimen and a jointed specimen can be classified into the following four  
Figure 13: Change in DSLR with the angles, \(\alpha\), of specimen with \(\beta\) = 39\({}^{\circ}\).  
types: (A) intact with or without tiny flakes, (B) slide failure, (C) fracture failure, and (D) crushing failure. Therefore, the relationship between dynamic peak stress and loading rate varies greatly.
2. The results of ANOVA indicate that the loading rate, the angle of the base plane (\(\beta\)), and asperity (\(\alpha\)) all affect the dynamic peak stress of jointed specimens when fracture failure occurs. When slide failure occurs, the dynamic peak stress of the jointed specimen is affected by loading rate and \(\beta\), when the specimen is crushed to failure, the loading rate is the sole factor that significantly influences its dynamic peak stress.
3. The slope of the relationship between the dynamic peak stress and the loading rate, and the upper limit of the dynamic peak stress under slide failure of the planar joint specimen, are both smaller than those of the sawteeth joint specimen when the loads that are applied on joint surface have similar maximum angles. The slope of the relationship between the dynamic peak stress and the loading rate under fracture failure for the planar joint specimen is close to that for the sawteeth joint specimen. The small sawtooth with \(\alpha\leq 6^{\circ}\) provides additional friction on the surface of jointed specimen under slide failure. No slide failure is observed for the specimen with \(\alpha>6^{\circ}\).
4. Increasing angle \(\alpha\) increases the DSLR of the jointed specimen at slide failure, and this effect is influenced by the angle \(\beta\) of the specimen and the associated failure type. The angle \(\alpha\) insignificantly affects the DSLR when the jointed specimen is crushed to failure.
5. The dynamic peak stress of a specimen increases with the loading rate at a gradually decreasing rate. The \(\beta\) and \(\alpha\) of the jointed specimen affect the location of stress concentration during loading, further influencing the dynamic peak stress for specimens under slide failure and fracture failure. When the loading rate is high and the specimen is crushed to failure, the influences of \(\beta\) and \(\alpha\) disappear. Increasing the loading rate reduces the efficiency of increase of dynamic peak stress.  
T.-T.W.; Formal analysis, P.-Y.S.; Funding acquisition, T.-T.W.; Investigation, P.-Y.S. and C.-Y.L.; Project administration, P.-Y.S.; Resources, H.-H.L., T.-W.C. and T.-H.U.; Validation, P.-Y.S.; Writing - original draft, P.-Y.S.; Writing - review & editing, T.-T.W. All authors provided critical feedback and helped shape the research, analysis and manuscript. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors would like to thank the Ministry of Science and Technology, Taiwan, for financially supporting this research under contracts NSC 102-2221-E-027-071-MY3 and MOST-105-2116-M- 027-002.  
The authors declare no conflict of interest.