부산대학교 도서관

It is the purpose of the present paper to present a theoretical model of cutting slots with a steady highpressure water jet and a comparison with experiments. It order to predict the depth of the slot for both metal and rock, slot cutting has been described by one-dimensional excavation model. The progressive excavation of a rectangular element, illustrated in Fig. 6, has been analyzed, basing on the 6th power law on erosion which is experimentally formulated in the previous paper. In the present theoretical model, the depth of the slot is analytically solved by integrating the excavation speed of the rectangular element, defined by eq.(2), over the time of exposure, considering the effect of the pressure attenuation with the excavation.The theory and experiments show that the depth of the slotis a function of the nozzle diameter, the driving pressure, the time of exposure, i. e. number of passes times the width of the rectangular element divided by the traversing velocity, the pressure attenuation constants and the standard erosion pressure that characterizes the objective materials. The main conclusion is that the standard erosion pressure of a rock is closely connected to its mechanical strength and nearly equal to the tensile strength of the rock. From that, it has been successfully verified, as shown in Fig. 12, that the theory agrees well with the single cutting experiments summarized in Table 1.