fracturation par choc

CONT: ... another possible way of creating permeability in hot dry rocks is «impact fracturing». This method ... [may be described in its principle.] A bore, cased except near the lower extremity, is surmounted by a hydraulic accumulator, filled with water and pressurized by means of a pump until the accumulator weight is lifted. The lifting pressure should be perhaps about 90% of the estimated hydro-fracturing pressure. A dynamic blow would then be struck upon the top of the water column by means of some device resembling a pile-driver, so that shock waves would travel to the base of the bore and be reflected up and down at attenuating intensity. Very high instantaneous pressures would be generated which would fracture the rock, and it is expected that the steepness of the pressure rise would be such as to resemble explosive action, so that the «star» formation ... would be produced.