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

• Published in: Rock mechanics and rock engineering Vol. 58; no. 6; pp. 5981 - 6006
• Main Authors: Gao, Yanan, Zhang, Yao, Su, Benyu, Tan, Dengpan, Yang, Bengao, Gao, Mingzhong
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.06.2025; Springer Nature B.V
• Subjects: Civil Engineering; Computed tomography; Cracks; Damage; Dredging; Earth and Environmental Science; Earth Sciences; Electrical resistivity; Energy conservation; Excavation; Finite element method; Fracture mechanics; Geophysics/Geodesy; Image processing; Irradiation; Logarithms; Medical imaging; Microcracks; Microwave radiation; Multilayers; Original Paper; Pallets; Pores; Quantitative analysis; Rock excavation; Rocks; Sandstone; Scanning; Sedimentary rocks; Tomography; Visualization; Pores and micro-cracks; CT scanning; Microwave fracturing; Electrical resistivity; Mesoscopic mechanism
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-025-04456-1

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 (LGER max ), the proportion in area of high electrical resistivity region (HERR), the minimum logarithm of the ER (LGER min ), 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. Highlights Computed tomography scanning and image processing are employed to reconstruct and quantify the pores and micro-cracks within microwave-treated specimens. Electrical resistivity testing is used in conjunction with finite-element inversion to provide visualization and analysis for pores and micro-cracks. The impact of microwave irradiation on the meso-structure of sandstone is discussed comprehensively by comparing computed tomography and electrical resistivity results.