ABSTRACT
Blasting is one of the most economical splitting techniques in terms of the required time and cost. However, its application is occasionally limited by strict legal regulation of the use of explosives and generates adverse vibration effects on surrounding environment. When this limitation is imposed on insitu splitting, static rock splitting techniques such as those using a fracturing agent or hydraulic breaker have generally been used. However, these techniques are time-consuming and thus increase the splitting cost. To solve this problem, an alternative splitting technique termed the electric discharge impulse crushing method (EDICM) was developed by Hitachi Zosen Corporation (Sasaki et al. 2009). The advantage of the technique is that the required splitting time is roughly several hundred micro-seconds and its application is not strictly regulated by law in most countries, especially in Japan. Figure 1 shows an example configuration for EDICM. The system consists of a power generator (200V), an electric discharge impulse generator with a maximum voltage of 6000V, a discharge cable and a discharge cartridge with a scale of several centimeters. A thin metal wire is installed in the cartridge filled with a self-reactive liquid. The cartridge is set in a borehole drilled in the splitting target such as rock or concrete. The voltage for the electric discharge impulse generator, size of the cartridge and amount of the self-reactive liquid are flexibly changed depending on the purpose. In EDICM, two predominant pressures
are generated. First, the condenser is charged to high voltage in the system and electric energy is supplied to the thin metal wire in the cartridge, which generates plasma. With vaporization of the wire by the plasma, the first impulse pressure is generated.Then high pressure gas is generated by the reaction of the self-reactive liquid with the vaporization of the wire, which crushes the rock or concrete. Although the applicability of EDICM to various purposes such as rock and concrete splitting has been verified, the optimum design for such purposes is not yet clear. Thus we investigated the fracture process in EDICM by using the dynamic fracture process analysis (DFPA) code. This analysis code is based on the dynamic finite element method considering the crack propagation, material inhomogeneity and fracture process zone. The details were discussed by Cho (2003). Here, considering the
generated pressure waveform, i.e. loading rate, is a significant factor for the dynamic fracturing process (Cho et al. 2004), and characterization of generated pressure in EDICM is indispensable. Thus our aim in this paper is to model the characteristics of pressure generation due to EDICM for DFPA and to obtain knowledge for simulating rock splitting with EDICM.
