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<p>Microwave fracturing and assisted mechanical breakage hold great potential for efficiency enhancement and energy conservation of hard rock excavation. However, the mechanism of microwave-assisted rock breaking has not yet been comprehensively revealed. In this study, the sandstone specimens are initially treated with the microwave power level of 1–5&#xa0;kW. Subsequently, computed tomography (CT) scanning and image processing are employed to reconstruct and quantify the pores and micro-cracks within microwave-treated specimens. Afterward, electrical resistivity (ER) testing is used in conjunction with finite-element inversion to provide visualization and quantitative analysis for the connectivity of pores and micro-cracks. The conclusions are as follows: (1) the formation of macro-cracks induced by microwave irradiation can be attributed to the connection and penetration of pores and micro-cracks. It always initiates from the surface and propagates towards the interior. An increase in microwave power level results in a more extensive and complex distribution of microwave cracks within specimens. (2) Microwave triggers the distribution of ER transform from irregular into nearly multi-layer circular. With the increase in the duration of microwave irradiation, the maximum logarithm of the ER (LGER<sub>max</sub>), the proportion in area of high electrical resistivity region (HERR), the minimum logarithm of the ER (LGER<sub>min</sub>), and the proportion in area of low electrical resistivity region (LERR) all exhibit a parabolic trend. These indicators reach their extremums after irradiation for about 2/3&#xa0;T. (3) The ER of specimens is significantly influenced by microwave energy. High microwave power levels (≥ 3&#xa0;kW) have the potential to intensify damage within the interior of specimens, while increased microwave energy can enhance damage on the surface of specimens. (4) There is a stress equilibrium area at the center of the microwave-treated specimen, i.e., the stress is close to zero. In addition, the mechanism of microwave-assisted rock breaking is discussed from a mesoscopic perspective.</p>

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Mesoscopic Fracture Mechanism of Sandstone Subject to Microwave Irradiation: Insights from CT Scanning and Electrical Resistivity Testing

  • 期刊论文

  • 发表日期：

    2025年3月3日

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  • Yanan Gao,
  • Yao Zhang,
  • Benyu Su,
  • Dengpan Tan,
  • Bengao Yang,
  • Mingzhong Gao

摘要

Microwave fracturing and assisted mechanical breakage hold great potential for efficiency enhancement and energy conservation of hard rock excavation. However, the mechanism of microwave-assisted rock breaking has not yet been comprehensively revealed. In this study, the sandstone specimens are initially treated with the microwave power level of 1–5 kW. Subsequently, computed tomography (CT) scanning and image processing are employed to reconstruct and quantify the pores and micro-cracks within microwave-treated specimens. Afterward, electrical resistivity (ER) testing is used in conjunction with finite-element inversion to provide visualization and quantitative analysis for the connectivity of pores and micro-cracks. The conclusions are as follows: (1) the formation of macro-cracks induced by microwave irradiation can be attributed to the connection and penetration of pores and micro-cracks. It always initiates from the surface and propagates towards the interior. An increase in microwave power level results in a more extensive and complex distribution of microwave cracks within specimens. (2) Microwave triggers the distribution of ER transform from irregular into nearly multi-layer circular. With the increase in the duration of microwave irradiation, the maximum logarithm of the ER (LGERmax), the proportion in area of high electrical resistivity region (HERR), the minimum logarithm of the ER (LGERmin), and the proportion in area of low electrical resistivity region (LERR) all exhibit a parabolic trend. These indicators reach their extremums after irradiation for about 2/3 T. (3) The ER of specimens is significantly influenced by microwave energy. High microwave power levels (≥ 3 kW) have the potential to intensify damage within the interior of specimens, while increased microwave energy can enhance damage on the surface of specimens. (4) There is a stress equilibrium area at the center of the microwave-treated specimen, i.e., the stress is close to zero. In addition, the mechanism of microwave-assisted rock breaking is discussed from a mesoscopic perspective.