Mechanical responses and fracture mechanism of rock with different free surfaces under the chisel pick cutting

With the increasing demand of the shipping infrastructure projects such as ports and waterways, it is urgent to improve the rock cutting ability and applicable range of trailing suction hopper dredgers. A rock breaking method using free surfaces to assist the draghead is proposed. Verified by experimental results, a series of numerical investigations were carried out to analyze the rock fracturing and cutting process. The rock cutting model by single chisel pick is developed using the LS-DYNA with a rock damage constitutive model, and the results are consistent well with the experimental data. The results show that the cutting force fluctuates with time, the large periodic fluctuations indicate the formation of large chips, and the short fluctuation period means the formation of small fragments. Moreover, with the assistance of free surface, the rock is not limited by the sidewall friction, and the cracks of rock are more likely to expand forward, thereby forming larger chips. Besides, it is found that the slit position and size play important roles in the rock fracture process. Based on all cutting performance parameters, the optimal slit position range is 25–35 mm, the optimal slit depth is 10 mm, which is half of the cutting depth, and the reasonable range of slit width should be 2–5 mm. Finally, a novel saw blades and chisel pick combined cutting method for rock is designed for further engineering application.