水噴流による岩石穿孔中チッピングの機構

概要

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A specific fixed depth chipping experiment is conducted to investigate the mechanism of chipping upon water jet drilling in rocks. It is shown that the net impinging time: t for a fixed depth chipping is closely associated with the bottom incident pressure: p evaluated by the Third Power Method, and that the fixed depth chipping occurs in the case that the bottom incident pressure: p is greater than a thresholding pressure: p th. The relation of p - t determined by the experiment is explained, basing on the fracture mechanics, and it is discussed that the chipping upon drilling is a kind of the fatigue fracture and initiates at a circumference of the advancing bottom. In order to forecast the incidence of the chipping upon water jet drilling, a chipping potential is subsequently proposed as a function of p and pth. It is clarified that the chipping potential PC in the case of p = pth = Se, where Se: the erosion strength of materials, is available for forecasting the incidence of chipping upon drilling.
2000-11-25