PSI - Issue 2_A

Koji Uenishi et al. / Procedia Structural Integrity 2 (2016) 350–357 Uenishi et al. / Structural Integrity Procedia 00 (2016) 000–000

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4. Conclusions

Dynamic fracture patterns generated by electric discharge impulses (EDI) in the field experiments may be reproduced by the developed three-dimensional wave simulator for a PC. Here, instead of employing alternately charged holes, more complex geometry for the positions of blast and dummy holes have been prepared: Dummy holes are not placed on the expected main crack path (fracture plane) and they are set rather to direct the main crack to connect the blast holes only. Note that our current method is aimed more for critical situations to construct and destruct (parts of) structures made of geomaterials in urban areas, which requires a very careful approach (No explosive can be used in such populated regions; Absolutely no damage to the surroundings is allowed, etc.) and a complex three dimensional treatment is acceptable in actual fracture operation. We believe this is quite a new topic also in the field of fracture mechanics, and also, it is important first to know whether the knowledge accumulated through our experience with, say, blasting by detonating explosives, is still valid for the modern safer technology (controlled dynamic destruction by application of EDI) or not. Through this study, it has been recognized that geometrical settings (positions of holes and planes of weakness in structures) may play an important role in controlling fracture extension and this characteristic may be utilized to realize more efficient disintegration of a given structure. For more controllable structural fracture and demolition, the simulation technique (possibly with more refined fracture criteria) may be used to design optimal positions of blast and dummy holes in the structures. Acknowledgements The technical support for the field experiments, provided by the Hitachi Zosen Corporation (now Nichizo Tech Inc.), is kindly acknowledged. References Andres, U., 1989. Parameters of Disintegration of Rock by Electrical Pulses. Powder Technology, 58, 265–269. Bluhm, H., Frey, W., Giese, H., Hoppe, P., Schultheiss, C., Straessner, R., 2000. Application of Pulsed HV Discharges to Material Fragmentation and Recycling. IEEE Transactions on Dielectrics and Electrical Insulation, 7, 625–636. Cotterell, B., Rice, J.R., 1980. Slightly Curved or Kinked Cracks. International Journal of Fracture, 16, 155–169. Fukuda, D., Moriya, K., Kaneko, K., Sasaki, K., Sakamoto, R., Hidani, K., 2013. Numerical Simulation of the Fracture Process in Concrete Resulting from Deflagration Phenomena. International Journal of Fracture, 180, 163–175. Hofmann, J., Weiss, Th. G. G., 1997. Pulsed Power Technologies for Commercial Material Reduction and Crushing Applications. Digest of Technical Papers-IEEE International Pulsed Power Conference, 1, 203–207. Kencanawati, N. N., Shigeishi, M., 2011. Acoustic Emission Sources of Breakdown Failure due to Pulsed-Electric Discharge in Concrete. Construction and Building Materials, 25, 1691–1698. Lisitsyn, I.V., Inoue, H., Katsuki, S., Akiyama, H., Nishizawa, I., 1999. Drilling and Demolition of Rocks by Pulsed Power. Digest of Technical Papers-IEEE International Pulsed Power Conference, 1, 169–172. Narahara, S., Namihira, T., Nakashima, K., Inoue, S., Iizasa, S., Maeda, S., Shigeishi, M., Ohtsu, M., Akiyama, H., 2007. Evaluation of Concrete made from recycled coarse aggregates by pulsed power discharge. Digest of Technical Papers-IEEE International Pulsed Power Conference, 1, 748–751. Rim, G. H., Cho, C. H., Lee, H. S., Pavlov, E. P., 1999. An Electric-Blast System for Rock Fragmentation. Digest of Technical Papers-IEEE International Pulsed Power Conference, 1, 165–168. Rossmanith, H. P., Uenishi, K., Kouzniak, N., 1997. Blast Wave Propagation in Rock Mass - Part I: Monolithic Medium. Fragblast, 1, 317–59. 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. Weise, Th. G. G., Loeffler, M. J., 1993. Experimental Investigations on Rock Fractioning by Replacing Explosives with Electrically Generated Pressure Pulses. Digest of Technical Papers-IEEE International Pulsed Power Conference, 1, 19–22.