Mechanism Analysis of Jet Drilling Rock by Numerical Simulation and Experiment

Abstract

Rock damage and breaking mechanism with water jet has been as yet a difficult problem due to jet high turbulence and complicacy of rock material. According to fluid-structure interaction (FSI) theory, the standard k-epsilon two equations and control volume method for water jet, and the elastic orthotropic continuum and finite element method for rocks, are employed respectively to establish a numerical analyzing model of high pressure water jet impinging on rock. A damage criterion, with non-dimensional coefficient to characterize rock damage, is also set up for analyzing rock failure mechanism with water jet. The process of jet impact on the rock is simulated, by using the FSI model, Micro failure mechanism test and analysis with scanning electron microscope (SEM) for rock failure surface by jets cutting were performed, whose results show that the micro-mechanism of rock failure due to water jet impingement is a brittle fracture in the condition of tensile and shearing stress. The test results also agree well with the numerical simulating analysis, which constructs a bridge between the micro-failure and macro-breaking mechanism of rock with water jets impact. The investigation affords a new method for studying the mechanism of rock failure underhigh pressure water jet impingement.