Water jet cutting technology is widely used to improve coal seam permeability and prevent gas outbursts. Increasing the jet flow rate could enhance effectiveness in coal-breaking. However, there is currently a lack of a foundation for optimizing parameters in high-flow water jet coal-breaking, particularly under conditions of a far jet target distance, limiting the improvement of coal-breaking efficiency. This research utilized an orthogonal experimental design for high-flow water jet experiments to investigate the influence of jet target distance, jet pressure, horizontal traverse velocity, and vertical oscillation velocity on coal mass removal rate. The research further integrated coal-breaking characteristics and the evolved law of mass removal rate to examine the impact of the factors, including jet velocity, jet action area, water cushion effect, total displacement of the jet, the jet impact energy per unit length and the number of up and down movements, on the trend of coal mass removal rate. The results showed that the influence of jet target distance, jet pressure, vertical oscillation velocity, and horizontal traverse velocity on the coal mass removal rate decreases in that order. Under varying jet parameters, the fragmentation of coal surface exhibits five patterns from local to large block detachment. Additionally, a regression model was established to predict the maximum coal mass removal rate. Based on the trend of the maximum mass removal rate, potential optimal parameters for enhancing the coal mass removal rate were proposed. These findings will provide a substantial foundation for advancing the efficiency of coal-breaking.

Coal,Water jet,Permeability enhancement,Mass removal rate,Orthogonal experiment