Integrated laser pre-treatment and impact loading method for enhanced underwater icebreaking

The extensive coverage of thick ice in polar regions imposes severe constraints on the efficiency and safety of resource extraction, maritime route development, and scientific exploration. However, existing icebreaking techniques are hindered by low operational efficiency, limited environmental adaptability, and poor ecological compatibility, rendering them inadequate for the complex conditions encountered in polar environments. Therefore, a novel underwater icebreaking method that combines laser pretreatment with impact loading is proposed. In this method, multipoint laser irradiation is initially employed to weaken the structural integrity of the ice, thereby facilitating its fragmentation under subsequent impact loading. Ultimately, efficient fracturing of ice up to 20 cm thick is achieved. A thermo-mechanical coupling model characterizing laser-ice interaction within underwater conditions is established. Numerical simulations of the temperature and stress fields under multi-point irradiation are performed. The thermodynamic mechanism by which laser energy weakens the structural integrity of the ice is elucidated. An experimental platform is constructed to validate the proposed method using natural freshwater ice. The influences of multi-point laser irradiation parameters on ice fragmentation performance are systematically investigated. Experimental results indicated that an outward-to-inward irradiation sequence significantly enhances the synergy between thermal and mechanical effects, thereby improving icebreaking efficiency. Furthermore, deployment spacing, laser power, and irradiation duration are identified as critical factors influencing the characteristics of ice fragmentation. Finally, the optimal parameter combination for efficient icebreaking is determined to be a deployment spacing of 4 cm, a laser power of 1703 W, and an irradiation duration of 15 s. This work provides theoretical insights and experiential support for the advancement of laser icebreaking technology.