An evaluation model and its application of low-pressure abrasive air jet slitting hard rock

Low-pressure abrasive air jet technology is one of the most promising methods for addressing the issues of low efficiency and significant tool wear in hard-rock drilling, owing to its strong rock-breaking capability and low energy consumption. However, the application of this technology faces challenges due to the reliance on single evaluation indices (e.g., slit depth, width, volume), which lack universality and generality, making it difficult to determine the optimal slit parameters under varying working conditions. This limitation significantly hampers the effectiveness of abrasive jet technology. To address this issue, proposes an evaluation model that integrates the quantitative relationships among slit parameters such as depth,width, and volume. A jet slit morphology distribution equation is derived through three-dimensional reconstruction and homogenization of rock slit morphology. The ratio of the mean area (A) of the slit morphology curve to the distribution function parameter (a₁) is defined as the characteristic width of the slit, denoted as b, and the ratio of b to a₁ is defined as the width-to-height ratio P. The effectiveness of the slit is evaluated using P, leading to the following conclusions: when P≤0.5, a narrower and deeper slit is formed; when P > 0.5, a wider and shallower slit is produced. By using P to characterize the slit effect under different parameter conditions, it is determined that when a deeper slit is required, the jet impact target distance should be maintained at 40 mm, the abrasive grain size should range between 60 and 90 mesh (0.16～0.25 mm), the abrasive hardness should exceed 7.0 on the Mohs scale, the mass flow rate of the abrasive should be between 16 g/s and 32 g/s, and an impact angle of 60° should be used. For obtaining a wide and shallow slit, the abrasive grain size should exceed 90 mesh (0.16 mm), the Mohs hardness should be less than 7.0, the abrasive mass flow rate should be lower than 8 g/s, the jet impact angle should be greater than 75°, and the distance between the jet and the target should be greater than 40 mm.