Numerical simulation and experimental research on sandstone breaking by abrasive water jet based on microscopic perspective

The ability of abrasive water jet (AWJ) to break rock is closely related to the material properties of the object being cut. In particular, sandstone, a typical "clastic + cement" structure, occupies a large proportion of the the coal measures. The conventional macroscopic study cannot accurately describe the complex process of its rock- breaking, and thus a more detailed study must be carried out from a microscopic perspective. This work established a numerical model of the AWJ broken sandstone based on a microscopic perspective, prepared artificial sandstone and conducted cutting tests to analyze the wall morphology after cutting. The study revealed the mechanism and differences between water jet (WJ) and AWJ in breaking sandstone, and explored the effects of different clastic sizes and mass fractions on the breaking effect. Numerical simulation results show that WJ mainly destroys the cement and is dominated by the erosion effect, while AWJ effectively destroys the cement and the clastics and improves the rock-breaking effect. Stress wave analysis shows that AWJ has a higher peak stress wave than WJ; as the mass fraction of clastic increases, the peak stress wave of AWJ decreases; as the size of clastic increases, the peak stress wave increases. Both experimental and numerical simulation results show that the rock-breaking capacity of AWJ is weakened with increasing clastic mass fraction and increasing clastic size. Observations of the cut wall morphology found that the forms of action of AWJ on sandstone include: grinding, transgranular fracture, embedding, replacement, and peeling actions. This study reveals the mechanism of sandstone breaking at microscopic perspective, providing a reference for optimizing the parameters and improving the efficiency of rock breaking, for AWJ.