• Explosives and Blasting
• /
• v.35 no.3
• /
• pp.15-20
• /
• 2017

In order to obtain the dynamic response behavior of the rock subjected to blasting loading, a shock-proof high sensitivity impact sensor which can measure high frequency dynamic force and strain events should be adopted. Because the impact sensors which uses quartz and piezoelectric element are costly, generally the strain measurement-based impact (SMI) sensors are applied to high speed loading devices. In this study, dynamic Brazilian tension tests of granitic rocks was conducted using the Nonex Rock Cracker (NRC) reaction driven-high speed loading device which adopts SMI sensors. The dynamic response of the granite specimens were monitored and the intermediate strain rate dependency of Brazilian tensile strengths was discussed.

• Explosives and Blasting
• /
• v.39 no.1
• /
• pp.10-21
• /
• 2021

Brittle materials such as rocks and concretes exhibit large strain-rate dependency under dynamic loading conditions. This means that the mechanical properties of such materials can significantly be varied according to load velocity. Thus, the strain-rate dependency is recognized as one of the most important considerations in solving problems of blast engineering or rock dynamics. Unfortunately, however, studies for characterizing the dynamic properties of domestic rocks and other brittle materials are still insufficient in the country. In this study, dynamic tensile tests were conducted using the Hopkinson pressure bar apparatus to characterize the dynamic properties of Geochang granite and high-strength concrete specimens. The dynamic Brazilian disc test, which is suggested by ISRM, and the spalling method were applied. In general, the latter is believed to have some advantages in experiments under high-strain rate deformation. It was found from the tests that there were no significant difference between the dynamic tensile strengths obtained from the two different test methods for the two materials given. However, this was not the expected result before the tests. Actually, authors expected that there be some differences between them. Hence, it is thought that further investigations are needed to clarify this results.