Dynamic Tensile Response of a Microwave Damaged Granitic Rock
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Dynamic Tensile Response of a Microwave Damaged Granitic Rock X. Li 1,2 & S. Wang 1 & K. Xia 1,2 & T. Tong 3 Received: 11 June 2020 / Accepted: 19 October 2020 # Society for Experimental Mechanics 2020
Abstract Background Understanding the dynamic tensile response of microwave damaged rock is of great significance to promote the development of microwave-assisted hard rock breakage technology. However, most of the current research on this issue is limited to static loading conditions, which is inconsistent with the dynamic stress circumstances encountered in real rock-breaking operations. Objective The objective of this work is to investigate the effects of microwave irradiation on the dynamic tensile strength, fullfield displacement distribution and average fracture energy of a granitic rock. Methods The split Hopkinson pressure bar (SHPB) system combined with digital image correlation (DIC) technique is adopted to conduct the experiments. The overload phenomenon, which refers to the strength over-estimation phenomenon in the Brazilian test, is validated using the conventional strain gauge method. Based on the DIC analysis, a new approach for calculating the average fracture energy is proposed. Results Experimental results show that both the apparent and true tensile strengths increase with the loading rate while decreasing with the increase of the irradiation duration; and the true tensile strength after overload correction is lower than the apparent strength. Besides, the overload ratio and fracture energy also show the loading rate and irradiation duration dependency. Conclusions Our findings prove clearly that microwave irradiation significantly weakens the dynamic tensile properties of granitic rock. Keywords Microwave irradiation . SHPB . Dynamic tensile response . Digital image correlation (DIC) . Overload correction . Average fracture energy
Introduction Microwave-assisted hard rock breakage has been considered as a promising technique to reduce the cutter wear and energy consumption when tunnelling in hard rock formations [1–4]. To better illustrate the weakening effect of microwave irradiation, numerous experimental studies have been conducted using different rocks such as ilmenite [5], granodiorite [6],
* K. Xia [email protected] 1
State Key Laboratory of Hydraulic Engineering Simulation and Safety, School of Civil Engineering, Tianjin University, Tianjin 300072, China
2
Department of Civil & Mineral Engineering, University of Toronto, Toronto, ON M5S 1A4, Canada
3
Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China
basalt [7], gabbro [8], granite and sandstone [9, 10]. Generally, the microwave-induced damage within the rocks results in rock strength reduction and thus facilitates hard rock breakage. Since rocks are considerably weaker in tension than in compression, an accurate understanding of the tensile response of microwave damaged rock is more crucial. However, the existing investigations on
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