Abstract

FRANGAKIS, T.; MOSS, E.A.  and  SKEWS, B.W.. The development of a hydraulic pulse generator for breaking rock in the mining industry. R&D j. (Matieland, Online) [online]. 1999, vol.15, pp.79-84. ISSN 2309-8988.

The aim of this research was to develop a non-explosive mining or quarrying device which fractures rock through the application of liquid pressure pulses into drilled holes, a process requiring a peak pressure of approximately 250 MPa, with a rise time of about 0.5 ms. A full-scale machine was designed, built and tested, using air for energy storage and a moving piston as the energy transfer medium. It utilises a double diaphragm mechanism to abruptly pressurise the back of an 80 kg piston of diameter 200 mm, which thereafter impacts with a further thin diaphragm enclosing water in a cavity (to simulate the hole in rock) comprising a thick-walled steel cylinder of internal dimensions 40 mm diameter × 1000 mm deep. An LVDT was used to monitor the piston displacement whilst a pressure transducer tracked the hole pressurisation. Measurements conducted over a range of gas precharge pressures corroborated satisfactorily with computational predictions. The device released approximately 18 kJ into the liquid section, with associated peak pressures in excess of 300 MPa and rise times of about 0. 7 ms, using the maximum gas precharge pressure of 9.2 MPA. Overall energy transfer efficiencies varied in the range 10% to 80%. In conclusion, the research validated the basic concept that large pressures for fracturing rock could be rapidly and efficiently generated through the impact of a moving mass on a column of water filling a hole.

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