Issue 50

L. He et alii, Frattura ed Integrità Strutturale, 50 (2019) 649-657; DOI: 10.3221/IGF-ESIS.50.55 649 Focused on Structural Integrity and Safety: Experimental and Numerical Perspectives Structural failure process of schistosity rock under microwave radiation at high temperatures Leping He, Yucheng Gu, Qijun Hu, Yuan Chen, Junsen Zeng School of Civil Engineering and Architecture, Southwest Petroleum University, Chengdu 610500, China 201231010028@swpu.edu.cn , guyucheng0728@163.com, huqijunswpu@163.com , 965742308@qq.com , zengjunsenwork@163.com A BSTRACT . The effects of high temperature induced by microwave radiation on the schistosity structural rock were investigated. A 1.45 kW commercial microwave system was employed to irradiate specimens to a designed temperature (300 − 800 °C) for 15 minutes. Cracking and local melting initially appeared in the biotite enrichment area at 500 °C. Macro-cracks in the dark area were parallel to the schistosity trend, owing to the weak connection in a direction perpendicular to the schistosity plane. The composition of the rock did not significantly change before and after microwave radiation. The diffraction peak intensity of the biotite decreased with temperature increase, owing to melting. The average peak stress decreased significantly with increasing temperature. It is concluded that the high temperature induced by microwave radiation promotes hard rock breakage and the schistosity structure of rock significantly affects the cracking pattern. K EYWORDS . Microwave radiation; Schistose granite; High temperature; Thermal damage. Citation: He, L., Gu, Y., Hu, G., Chen, Y., Zeng, J., Structural failure process of schistosity rock under microwave radiation at high temperatures, Frattura ed Integrità Strutturale, 50 (2019) 649-657. Received: 17.07.2019 Accepted: 11.09.2019 Published: 01.10.2019 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION ncreasing the efficiency of hard rock breakage is a common issue in mining, tunnelling, and nuclear waste disposal [1- 3]. Traditional hard rock breakage methods (such as mechanical excavation and blasting), are problematic because they consume much energy, are expensive, and contribute to pollution. Considering the characteristics of rapid volumetric heating, selective heating, and instantaneous control, microwave radiation is considered as a potential method for rock comminution processes. Since Maurer [4] suggested the usage of microwaves for rock breakage in the 1960s, many studies have demonstrated that microwave radiation could effectively reduce the mechanical performance of rocks [5-7]. Minerals can absorb microwave energy and convert it into heat energy. The dielectric properties of minerals determine the capacity for absorbing and converting microwaves [8,9]. Lu et al. [7] suggested that the microwave susceptibility of rock-forming minerals could be linked to the content of ferrum. Therefore, temperature gradients would be produced in the irradiated rock, reducing the strength of the rock by yielding micro- and macro-cracks [10-12]. The water content, the size and location of grains, can affect the initiation and propagation of cracks [13,14]. Also, the microwave radiation conditions, including the microwave I