Investigating Microwave Treatment of Rocks Based on Fracture Mechanics Analysis in Mode I Fracture Toughness Test

During the past decade, numerous research has been conducted to evaluate the effectiveness of microwave treatment in improving rock fragmentation. While these studies focused on investigating the effect of microwave treatment on rock parameters, the current research approaches the problem from another perspective by studying the applicability of mode I fracture toughness parameters to evaluate the effectiveness of the microwave treatment as a rock pre-conditioning method based on energy analysis. Different rock sizes are investigated, and it is shown that for the basalt rock used in this study, the minimum required diameter for the fracture toughness experiments is 70 mm. In a novel approach, a finite element based numerical model is employed to maximize the energy absorption of the sample in the cavity. It is shown that optimizing the location of the rock sample in the cavity can increase the heat over microwave efficiency (HOME) and weakening over microwave energy (WOME) by more than 40% and 30%, respectively. Furthermore, it is concluded that although increasing the exposure time results in more K IC value reduction, it decreases the WOME value by more than 50% in some cases. Finally, the applicability of fracture toughness experiments in evaluating the effectiveness of microwave treatment is discussed in detail.