Cutting efficiency of extremely hard granite by high-pressure water jet and prediction model of cutting depth based on energy method

Traditional mechanical rock breaking has problems such as low rock breaking efficiency and severe tool wear when encountering extremely hard granite. As the most easily implemented and promising new rock-breaking technology, high-pressure water jet technology can solve such challenges. However, achieving high-efficiency breaking of granite using high-pressure pure water jets has been an outstanding technical challenge. This paper takes granite, which is difficult to break in engineering, as the research object and explores its cutting efficiency subjected to high-pressure continuous water jet. The effects of key parameters such as jet pressure, traverse speed, nozzle diameter, standoff distance, and cutting times on cutting efficiency are focused. Through experiments, it is found that there are three different failure modes of rocks under water jet impact with different erosion energies. Brittle spalling is more likely to occur when the erosion energy is relatively low, forming wider kerf. The concept of depth specific energy (DSE) is put forward to represent the energy utilization rate of cutting depth, and the selection of the optimal jet parameters is given. When the traverse speed increases from 1 to 10 m min-1 and the cutting times increase from 1 to 5, the cutting depth and cutting width increase by 66.14% and 81%, respectively, while the DSE and cutting time decrease by 70% and 50%, respectively. A technological approach of high water pressure, high linear speed, and multiple cutting is proposed. At last, a novel depth prediction model for high-pressure water jet cutting granite is established based on the energy perspective, and the reliability and plausibility of the model are verified by experimental tests. The results of the study contribute to accelerating the application of water jet for breaking hard rock in engineering.