Blast-hole electro-fracture of concrete lumps

Abstract

The research data of concrete fracturing and splitting off of the free surface by borehole electro-blast with the discharge initiation by the wire explosion have been presented. The method is based on the initiation of a capillary discharge by the exploding wire inside the solid dielectric material1. The effectiveness of splitting off and fracturing of concrete depending on different combinations of the shock wave transfer media (gel, water and polyethylene) was determined. It is shown that the long mode of electrical energy release (T 0.5 = 36 µs) is more effective in comparison with the short one (T 0.5 = 18 µs) for the concrete splitting off. The combined usage of capillary discharge in the polyethylene and in the gel leads to the most effective fracturing of the solid material. With the pulse amplitudes of 13 kV and wire length of 100 mm concrete pieces of 15×15×30 cm could be split off. Specific energy deposition of ∼ 50 kJ/cm3 leads to the pressure build-up of ∼2.4·109 Pa in the plasma channel of capillary discharge. Under the action of pressure the highly conductive plasma channel expands and generates the shock wave, causing the mechanical stress formation in solid. The generator energy conversion into the plasma channel and into the wave of mechanical stresses in concrete has been considered. The dynamics of shock-wave propagation is investigated in condensed media polyethylene (gel)-concrete depending on the mode of plasma channel energy release.