Numerical and experimental analyses of rock failure mechanisms due to microwave treatment

Despite the extensive studies conducted on the effectiveness of microwave treatment as a novel rock pre-conditioning method, there is yet to find reliable data on the rock failure mechanisms due to microwave heating. In addition, there is no significant discussion on the energy efficiency of the method as one of the important factors among the mining and geotechnical engineers in the industry. This study presents a novel experimental method to evaluate two main rock failure mechanisms due to microwave treatment without applying any mechanical forces, i.e. distributed and concentrated heating. The result shows that the existence of a small and concentrated fraction of a strong microwave absorbing mineral will change the failure mechanism from the distributed heating to the concentrated heating, which can increase the weakening over microwave efficiency (WOME) by more than 10 folds. This observation is further investigated using the developed coupled numerical model. It is shown that at the same input energy, the existence of microwave absorbing minerals can cause major heat concentration inside the rock and increase the maximum temperature by up to three times.