a drilling method in which the rock at the bottom of a borehole filled with water is broken by a water hammer that is created by means of a high-voltage (up to 200 kilovolts) pulse discharge. The method was first developed in the USSR by L. V. Iutkin in the 1950’s.
The drill consists of a nonrotating tubular electrode and a rotating central electrode. High-voltage current pulses are supplied to the electrodes from the surface at a given rate. Electrical breakdown in the interelectrode gap occurs via the water. In the liquid, the expanding gas pocket of the breakdown creates the water hammer that breaks the rock at the bottom of the borehole.