Electrohydraulic rock fracturing by pulsed power generated focused shocks

The electrohydraulic effect for rock breaking and drilling was investigated using focused shocks. The multikilobar shocks were generated in the test chamber of an 80 kJ pulsed power facility. The latter consisted of an 80 kJ Marx bank connected to a water-filled chamber through four 1 MV pulse-forming lines (PPL). The PFLs were 3.35 /spl Omega/, coaxial, deioinized water lines, 3.66 m long. The pulse length was 0. 2- 1 /spl mu/s. The electrohydrodynamics of the arc discharge in water, the physics of the resulting shock waves and the rock fracture were analyzed theoretically and experimentally using one of the four PFLs. We were able to discharge 8 - 10 kJ energies in an arc, generated in tap water, in 100 ns. A series of such discharges has produced erosion rates of 0.25 cm/sec, in 6 cm holes in limestone and sandstone samples. At a repetition rate of one discharge per second, this rate is equivalent to 7 - 10 m/hour for an 8-inch hole.