The influence of minerals on the mechanism of microwave-induced fracturing of rocks

Microwave-induced rock fracturing technology is considered as a promising method for rock fragmentation and mineral processing. The borehole fracturing technology for hard rocks may be used to relieve stress on rock masses encountered in deep underground engineering works and prevent geological disasters triggered by high stress concentration. However, owing to microwaves causing selective heating, different types of rocks show different heating effects. Based on microwave heating experiments on multiple types of rocks, three typical rocks with different heating effects were investigated. According to X-ray diffraction (XRD) patterns and microscope images, the primary mineral compositions of rocks and microstructures of minerals were determined. By employing an infrared thermal imager, the distribution of surface temperature of samples were measured. Afterwards, according to sensitivity to microwaves and thermal expansion of rock-forming minerals, the mechanism whereby different types of rocks show different heating effects was analysed Chifeng basalt contains both minerals (pyroxene) sensitive to microwaves and minerals (olivine) with a high coefficient of thermal expansion, mainly manifesting itself as rock fracturing during microwave heating. As only minerals (pyroxene) sensitive to microwaves, while no minerals with high coefficients of thermal expansion were found in Anshan gabbro, the rock was mainly molten during microwave heating. Neither minerals sensitive to microwaves, nor minerals with a high coefficient of thermal expansion were contained in the Beishan granite, so these samples underwent no significant change before, or after, microwave irradiation (C) 2020 Elsevier B.V. All rights reserved.