PSI - Issue 13

Koji Uenishi et al. / Procedia Structural Integrity 13 (2018) 652–657 Uenishi et al. / Structural Integrity Procedia 00 (2018) 000 – 000

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two-) dimensional experiments, and even for two-dimensional cases, there is still no consensus about fracture criteria for kinking and branching of cracks (Cotterell and Rice, 1980; Uenishi and Rossmanith, 2002).

Fig. 3. Propagation and interactions of dynamic disturbances in a homogeneous, isotropic, linear elastic rectangular specimen, (a) the case IC 09/00 and (b) IC-10/00. Due to the symmetric nature of the problem, we show only contours of volumetric strain, a strain invariant, in the lower quarter part for the time at some 20, 60, 100 and 140  s after initiation of the simultaneous application of EDI. 4. Conclusions Our field fracture experiments using electric discharge impulses (EDI) and investigating the influence of empty dummy holes on dynamic wave and fracture development in rectangular concrete specimens have indicated that sets of blast holes surrounded by empty dummy holes may actualize main crack development in a controlled, desired fashion. The ongoing field experiments of dynamic fracture by application of EDI suggest that in solid structures containing planes of weakness, e.g. rock masses / concrete structures with reinforcing steels bars, cracks tend to propagate along planes of weakness and we can utilize this characteristic for more efficient destruction of given structures, for instance, removal of only RC (reinforced concrete) lining segments from the surroundings in underground structures. We need more detailed analyses to evaluate the effect of planes of weakness on dynamic structural disintegration. Acknowledgements Cotterell, B., Rice, J.R., 1980. Slightly Curved or Kinked Cracks. International Journal of Fracture 16, 155 – 169. Johansson, D., Ouchterlony, F., 2013. Shock Wave Interactions in Rock Blasting: The Use of Short Delays to Improve Fragmentation in Model Scale. Rock Mechanics and Rock Engineering 46, 1 – 18. Mohanty, B., 1990. Explosion Generated Fractures in Rock and Rock-Like Materials. Engineering Fracture Mechanics 35, 889 – 898. Rossmanith, H.P., Uenishi, K., Kouzniak, N., 1997. Blast Wave Propagation in Rock Mass - Part I: Monolithic Medium. Fragblast 1, 317 – 359. Rossmanith, H.P., Uenishi, K., 2006. On Size and Boundary Effects in Scaled Model Blasts - Fractures and Fragmentation Patterns. Fragblast 10, 163 – 211. Uenishi, K., Rossmanith, H.P., 1998. Blast Wave Propagation in Rock Mass - Part II: Layered Media. Fragblast 2, 39 – 77. Uenishi, K., Rossmanith, H.P., 2002. Stability of Dynamically Propagating Cracks in Brittle Materials. Acta Mechanica 156, 179 – 192. Uenishi, K., Takahashi, H., Yamachi, H., Sakurai, S., 2010. PC-Based Simulations of Blasting Demolition of RC Structures. Construction and Building Materials 24, 2401 – 2410. Uenishi, K., Yamachi, H., Yamagami, K., Sakamoto, R., 2014. Dynamic Fragmentation of Concrete Using Electric Discharge Impulses. Construction and Building Materials 67, 170 – 179. We would like to sincerely thank Nichizo Tech, Inc., for the technical support. References