Theoretical and experimental investigation of electro discharge destruction of non-conducting materials

Abstract

The results of electro-discharge fracture of large-size concrete samples with electrical breakdown initiation by the exploding wire are presented. In order to minimize the operating voltage of the pulse generator and to increase the discharge gap and hence the energy absorption by the plasma channel that leads to the fracture build-up, the electro-bursting cartridge (copper wire in polyethylene) was used. With the pulse amplitudes of ∼ (15–20) kV and wire length of ∼ (20–60) mm, concrete blocks of 700*450*300mm size can be fractured. Specific energy deposition of ∼ 60 kJ/cm3 leads to the pressure buildup of up to 2.5·109 Pa in the discharge plasma channel. Under the action of pressure, the highly conductive plasma channel expands and generates the shock wave, causing the mechanical stress formation in the solid. Elastoplastic deformations and radially propagating cracks are launched into the material and this leads to the sample fracture. The dynamics of the generator energy conversion into the plasma channel and into the wave of mechanical stresses in solid is considered. Electro-discharge fracture can be a cost-effective and practical solution for disintegration of the rock mass by splitting rock fragments off the free rock surface in mining, oil and gas, tunnel construction and similar applications.