Design and experimental verification of an underwater ultrasonic drill for rock exploration

Developing deep-sea drilling mechanisms based on new driving modes is important for promoting marine geological surveys and marine mineral resource exploration. We propose an underwater ultrasonic drill (UUD) for seabed rock drilling based on the piezoelectric driving principle and underwater rock-breaking mechanism. The driving device of the UUD was designed using piezoelectric vibration theory, and its performance parameters were predicted through simulations. A prototype of an ultrasonic drill suitable for underwater drilling was designed considering the working environment and drilling objects. To verify the drilling performance of the UUD, a drilling efficiency test system was set up, the influence law of key structural and dynamic parameters on drilling efficiency was studied using the orthogonal experiment method, and the optimal parameter combination was explored. The maximum drilling efficiency of UUD reached 32.29 mm/min in sandstone with a compressive strength of 20 MPa when the excitation frequency and voltage were 16,150 Hz and 780 V_P-P, respectively. The feasibility of UUD for rock drilling in the seabed was verified through comparison and power-testing experiments. Research on the UUD prototypes can provide new ideas for exploring deep-sea resources.