Title screen

An excavator adapted to break matters to be excavated, which exist in a deep hole made by excavation into which a discharge liquid is introduced, by the electric discharge between a plurality of electrodes which is generated by high-voltage pulses, characterized in that the excavator is provided with a high-voltage pulse generator, a plurality of electrodes, into at least one of which a high voltage from the high-voltage pulse generator is inputted, discharge liquid circulating systems and optimum condition setters; and an excavation method characterized by optimizing at least one of the parameters concerning the excavation efficiency, i.e. i) load voltage required to break matters to be excavated, ii) single pulse energy, and iii) quantity of discharge liquid by using the excavator so that the electric power consumption concerning the excavation becomes minimum. Concretely speaking, the optimum values of these parameters are estimated by equation, and the parameters are varied continuously or intermittently within the ranges of parameters including the estimated values in the vicinity of the centers thereof, whereby optimum values of the parameters are found out. In said equation, K represents a coefficient, n the number of electrodes, L a distance (cm) between electrodes, and Uo a numerical value obtainable by experiments, a voltage (kv) used when two electrodes placed on a surface of a sample to be excavated in a discharge liquid and spaced from each other at 1 cm break the sample.