Pulsed liquid jet for rock breaking

[Absent]: Rock fracture using continuous, high speed water jets is an existing technology used in the mining industry. However, it appears that a number of potential benefits can be derived by using pulsed liquid jet technique instead. Reductions in energy and water consumption should be possible because of improvements in efficiency associated with the pulsed water jet technique. However before a pulsed jet technique can be optimised and implemented in a practical system that yields the anticipated performance improvements relative to the continuous jet system, a thorough understanding of the physical processes involved needs to be obtained. This project endeavoured to gain a better understanding of pulsed jet technology by modifying the USQ gas gun to include a water reservoir downstream of the barrel which was used to generate a single, high speed water jet for analysis. A piston with a mass of approximately 55 grams was arranged to impact on the reservoir at different speeds up to 300 m/s. Pressures above 300 MPa were generated in the water reservoir when the piston was decelerated, and these pressures were sufficient to generate a single pulsed water jet at speeds over 1000 m/s. High speed photography was used to visualise the establishment of the high speed water jet and analyse the characteristics of the pulse. The pulse impacted on a strike plate which was attached to a vertical brass tube that extended to the floor. The brass tube was instrumented with strain gauges to characterise the high speed water jet. A pressure transducer was used at low pressures to determine the magnitude of the pressure pulse in the water reservoir. This data was then correlated with data recovered from the brass tube to establish a relationship between the two