Experimental study on rock breaking by single chisel pick under deep-sea hydrostatic pressure

Mineral cutting and breaking is the first step in deep-sea mining. To investigate the effects of hydrostatic pressure on the rock cutting process, this study analyzed cutting force, specific energy (SE), and debris distribution parameters (coarseness index CI, debris size parameter de, debris size uniformity n, fractal dimension D) under hydrostatic pressures of 0–12 MPa using a self-designed deep-sea rock cutting test bench. The relationships between SE and debris distribution parameters were further analyzed. The experimental results showed that cutting force and SE increased significantly with increasing hydrostatic pressure, the maximum cutting force and SE were increased to 7 and 25 times the corresponding values under atmospheric conditions, respectively. The increase of hydrostatic pressure caused the rock debris size to gradually decrease, but the debris uniformity first decreased and then increased. Higher CI and de, indicated smaller SE. Meanwhile lower n and D, demonstrated smaller SE. CI was identified as a reasonable debris distribution parameter that could be utilized to analyze rock breaking efficiency. This research provides insights into the rock breaking mechanism and offers experimental data and guidance for the design and simulation for deep-sea mining equipment.