Abstract
Mechanical excavation in hard or very hard rocks is still challenging in rock engineering. One plausible solution is to reduce rock strength prior to mechanical excavation to increase excavation and cost-efficiency. The present study utilizes a 6 kW microwave to irradiate rock specimens and evaluates the variation in rock strength and indentation hardness. Since the contact between the drill bits of roadheaders and the rock surface is a dynamic impact process, dynamic tests are conducted and compared with the quasi-static results. The experimental results demonstrate that short microwave irradiation (30 s) can produce substantial damage to the rock. The reduction of uniaxial compressive strength, Brazilian tensile strength, and indentation hardness under quasi-static loading can be about 39%, 43%, and 44%, respectively, and 33%, 26%, and 50%, respectively, under dynamic loading. In addition, it is found that the tensile strength is the most sensitive to microwave, while the crack density is the least sensitive. More importantly, this reduction is not linear and not monotonic to the irradiation time. The fast reduction of rock strength and indentation hardness after microwave irradiation implies the reduction in the drill-bit wear and increase in the excavation rate, and vigorously demonstrates the great potential of microwave-assisted mechanical excavation of hard or very hard rocks.
Highlights
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The dynamic indentation test is used to simulate the impact between drill bits and rock surfaces.
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Short microwave irradiation (30 s) can largely reduce the diorite strength and indentation hardness.
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The reduction is not linear and not monotonic to the irradiation time, regardless of loading rates.
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Different physical properties have different sensitivities to the microwave.
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Experimental results demonstrate the great potential of the microwave technique in hard rock excavation.
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Readers are welcome to request source data obtained the present experiments.
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Acknowledgements
The authors are grateful for the assistance and the data processing suggestions provided by the team member Dr. Gonglinan Wu and Mr. Zhijie Wang from Monash University, and Mr. Shuo Yang from Nanjing University. This work is supported by the National Natural Science Foundation of China (Grant Nos. 41831281, 52104121), the Innovative and Entrepreneurial Team Program of Jiangsu Province, China (JSSCTD202140), and the State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining & Technology (SKLGDUEK2115).
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Zou, C., Quan, X., Ma, Z. et al. Dynamic Strength and Indentation Hardness of a Hard Rock Treated by Microwave and the Influence on Excavation Rate. Rock Mech Rock Eng 56, 4535–4555 (2023). https://doi.org/10.1007/s00603-023-03243-0
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DOI: https://doi.org/10.1007/s00603-023-03243-0