Rao Pingping, Ouyang Peihao, Nimbalkar Sanjay, Chen Qingsheng, Cui Jifei, Wu Zhilin
Department of Civil Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200092, China.
School of Civil and Environmental Engineering, University of Technology Sydney, 15 Broadway, Ultimo, Sydney, NSW 2007, Australia.
Materials (Basel). 2022 Mar 16;15(6):2188. doi: 10.3390/ma15062188.
This work aims to investigate and analyse the mechanism of rock failure under high-voltage electropulses in order to evaluate and increase the efficiency of high-voltage pulse technology in geological well drilling, tunnel boring, and other geotechnical engineering applications. To this end, this paper discusses the equivalent circuit of electric pulse rock breaking, the model of shock wave in electro channel plasma, and, particularly, the model of rock failure in order to disclose the rock failure process when exposed to high-voltage electropulse. This article uses granite as an example to present an analytical approach for predicting the mechanical behaviour of high-voltage electropulses and to analyse the damage that occurs. A numerical model based on equivalent circuit, shock wave model, and elasto-brittle failure criterion is developed for granite under electropulse to further examine the granite failure process. Under the conditions described in this study, and using granite as an example, the granite is impacted by a discharge device (Marx generator) with an initial voltage that is 10 kV and a capacitance that is 5 µF before it begins to degrade at about 40 µs after discharge, with the current reaching its peak at approximately 50 µs. The shock wave pressure then attains a peak at about 70 µs. Dense short cracks form around granite and the dominant cracks grow to an average length of about 20 cm at around 200 µs. The crack width is predicted to be approximately 1.6 mm. This study detects dense cracks in a few centimetres surrounding the borehole, while around seven dominant cracks expand outward. The distribution of the length of the dominating cracks can be inhomogeneous because of the spatial heterogeneity of granite's tensile strength, however the heterogeneity has an insignificant effect on the crack growth rate, total cracked area, or the number of main cracks. The mechanism of rock failure under electropulse can be well supported by the findings of numerical simulations and analytical studies.
这项工作旨在研究和分析岩石在高压电脉冲作用下的破坏机制，以评估和提高高压脉冲技术在地质钻井、隧道掘进及其他岩土工程应用中的效率。为此，本文讨论了电脉冲破岩的等效电路、电通道等离子体中的冲击波模型，特别是岩石破坏模型，以揭示岩石在高压电脉冲作用下的破坏过程。本文以花岗岩为例，提出了一种预测高压电脉冲力学行为的分析方法，并分析了所产生的损伤。基于等效电路、冲击波模型和弹脆性破坏准则，建立了花岗岩在电脉冲作用下的数值模型，以进一步研究花岗岩的破坏过程。在本研究所述条件下，以花岗岩为例，花岗岩在放电装置（马克思发生器）的作用下受到冲击，初始电压为10 kV，电容为5 μF，在放电后约40 μs开始降解，电流在约50 μs达到峰值。冲击波压力随后在约70 μs达到峰值。花岗岩周围形成密集的短裂纹，主导裂纹在约200 μs时平均长度增长到约20 cm。裂纹宽度预计约为1.6 mm。本研究在钻孔周围几厘米范围内检测到密集裂纹，同时约有七条主导裂纹向外扩展。由于花岗岩抗拉强度的空间非均匀性，主导裂纹长度的分布可能不均匀，然而这种非均匀性对裂纹扩展速率、总裂纹面积或主裂纹数量的影响不显著。数值模拟和分析研究的结果能够很好地支持电脉冲作用下岩石破坏的机制。
