A New Prediction Model for Cutting Depth of Hard Rock Using High-Pressure Water Jets

High-pressure pure water jet has been widely used in breaking soft rocks and medium–hard rocks, but its research on cutting hard rocks is very limited. The cutting depth, as the most important index for evaluating the effectiveness of rock breaking by water jet, is difficult to be predicted accurately because of numerous influencing factors. This article aims to establish a concise and universal prediction model for the cutting depth of hard rock, including all variables that affect the cutting depth. Firstly, four types of granite and sandstone, which are difficult to break in engineering, are selected to investigate their cutting depth under the action of high-pressure continuous water jets. The rock physico-mechanical parameter that has the highest correlation with the cutting depth is found to be the shear modulus through tests. In order to reasonably evaluate the energy utilization rate of cutting depth of rock by water jet, the concept of cutting depth energy index (CDEI) is proposed. The jet pressure corresponding to the maximum value of CDEI is approximately 40–60