A study on the slot cutting in rocks with high-speed waterjets both in air and in water. (2nd Report). An empirical formula on the depth of cut for slot cutting in rocks with high-speed waterjets.

It is necessary to establish the empirical formula on the depth of cut for slot cutting in rocks with high-speed waterjets both in air and in water in order to apply the high-speed waterjets technology to various engineering fields such as tunnelling, pre-cracking around a deep borehole and rock excavation at the sea bottom as well as quarrying rocks.In this paper, to clarify the effects of standoff distance up to its limit where no cutting occurs and nozzle diameter from 1 to 2 mm on the depth of cut in rocks, systematic experiments were carried out both in air and in water for welded tuff and a comprehensive empirical formula on the depth of cut in rocks was proposed from the test results and those from a previous work.Main results obtained in this study are summarized as follows:1) There exists a limit of standoff distance beyond which no cutting occurrs for both in air and in water. The limit of standoff distance increases with both driving pressure and nozzle. diameter, and becomes much smaller in water in comparison with in air.2) The depth of cut depends on the distance from the limit of standoff distance rather than standoff distance itself.3) The critical pressure is almost independent of both standoff distance and nozzle diameter.4) The following formula is proposed as a comprehensive empirical formula on the depth of cut h for slot cutting in rocks both in air and in water.h=k(1-L/L0)γdβV-n (p-pc).where L is standoff distance, L0 is the limit of standoff distance, d is nozzle diameter, V is traverse rate, p is driving pressure, pc is critical pressure, and k, γ, β and n are coefficients which depend on environmental medium and rocks.