Comparative research of rock breaking by heat effect of continuous and pulse laser with experiment and simulation

Abstract

Laser rock breaking is a novel rock breaking technology to raise the rock breaking efficiency in deep and ultra-deep strata. Continuous and pulse lasers are two types of laser that are usually used in laser rock breaking research at present. However, the present studies’ main focus is on the breaking mechanism and character optimization of continuous laser. Studies to pulse laser and the differences between the two types of laser are rarely reported. The pulse and continuous laser with 800 W power were used in the laser rock breaking experiment, and the morphology of ablation pits was measured and compared. Then, a FEM simulation model was established by the results of the experiment. The distribution condition and the evolution process of temperature, ablation pit, yield condition, and equivalent strain at test points generated by two types of laser were measured and compared. The experiment results show a thick enamel layer covering the ablation pit generated by the continuous laser, which referring a higher ablation ability but with a shallower ablation pit in measurement. And the simulation results not only represent the higher ablation ability of continuous laser at the end of simulation but also show the circular heating–cooling process, stepping expansion process of ablation pit, faster ablation pit generation speed (0.03 s earlier), higher yield volume, and higher equivalent plastic strain (about three times higher) in radiated part with a pulse laser. Referring that it has higher ablation ability in short radiation time, stronger thermal stress effects on the radiated part, and less molten materials generated in the laser rock breaking process than continuous laser. This research can offer some references to the laser type selection in laser rock breaking and explain the rock breaking theory more comprehensively.