Enhanced rock breakage by pulsed laser induced cavitation bubbles: preliminary experimental observations and conclusions

Abstract

High-power laser has been considered as a potential method of rock breakage through melting. However, high energy consumption and low efficiency are the main restrictions for applying laser technology in rock excavation and fragmentation. A new rock breakage method which combines pulsed laser and induced cavitation is described in this paper, with potentially low energy consumption and high efficiency in rock fracturing. Cavitation is the rapid formation and collapse of vapour bubbles within a liquid. The irradiation of a pulsed laser beam with the energy density beyond the breakdown threshold of a liquid could induce cavitation bubbles in the liquid. The energy of the laser beam converts into highly pressurised cavitation bubbles. When the cavitation bubbles explode near rock surface, the explosions induce dynamic force to break the rock. In this paper, a series of tests using continuous and pulsed laser beams to break rocks in both air and water are presented. It is found that the pulsed laser in water produced the best rock-breaking efficiency without melting the rocks. Further analysis of the crater morphology and mechanical properties suggests the dynamic force at cavitation bubble explosion is the main cause of rock fracturing. The study leads to the conclusion that the pulsed laser induced cavitation in water is potentially an effective way for laser rock cutting technology with industrial applications.