郭军,米鑫程,冯国瑞,等. 基于液电效应的高压电脉冲岩体致裂特征及机理[J]. 煤炭学报,2024,49(5):2270−2282. doi: 10.13225/j.cnki.jccs.2023.0194
引用本文: 郭军,米鑫程,冯国瑞,等. 基于液电效应的高压电脉冲岩体致裂特征及机理[J]. 煤炭学报,2024,49(5):2270−2282. doi: 10.13225/j.cnki.jccs.2023.0194
GUO Jun,MI Xincheng,FENG Guorui,et al. Characteristics and mechanism of rock fracturing caused by high voltage electric pulse rock mass based on electrohydraulic effect[J]. Journal of China Coal Society,2024,49(5):2270−2282. doi: 10.13225/j.cnki.jccs.2023.0194
Citation: GUO Jun,MI Xincheng,FENG Guorui,et al. Characteristics and mechanism of rock fracturing caused by high voltage electric pulse rock mass based on electrohydraulic effect[J]. Journal of China Coal Society,2024,49(5):2270−2282. doi: 10.13225/j.cnki.jccs.2023.0194

基于液电效应的高压电脉冲岩体致裂特征及机理

Characteristics and mechanism of rock fracturing caused by high voltage electric pulse rock mass based on electrohydraulic effect

  • 摘要: 基于液电效应的高压电脉冲致裂技术是一种新型的岩体致裂技术,具有安全高效、绿色环保、能量可控等特点,在煤矿井下围岩应力调控方面拥有广阔的应用前景。由于井下岩体往往处在较为复杂的应力环境,为深入研究该技术在井下不同围岩应力环境下对坚硬岩体的致裂效果,通过LS-DYNA软件对基于RHT损伤本构模型建立的岩石试样进行高压电脉冲岩体致裂数值模拟试验,对岩体内部的损伤和有效应力演化过程进行采集,分析岩体的致裂特征及其裂缝扩展机理,通过数值模拟弥补在室内试验中因放电过程快、电磁干扰大而导致的致裂过程中岩体内部难以有效监测的问题。利用自主研发的高压电脉冲岩体致裂试验平台,开展了不同围岩应力条件下的高压电脉冲岩体致裂试验,通过获得的岩体表面破裂特征验证数值模拟结果的可靠性。获得以下结论:① 基于RHT本构模型建立了LS-DYNA高压电脉冲岩体致裂数值模型,根据炸药爆破与高压电脉冲的能量等效关系,构建了高压电脉冲数值模拟等效参数。通过实验室试验与数值模拟结果进行对比,验证了数值模型与等效参数的可靠性;② 对试样上表面裂纹扩展情况进行分析,发现裂纹会向最大压初始应力方向偏转。在此过程中,裂纹总长度先是逐渐减小。当所有裂纹与最大初始压应力夹角均小于45°时,裂纹总长度开始逐渐增大;③ 通过数值模拟,发现在致裂初期,高压电脉冲放电产生的动态应力远大于围岩应力,对试样的破坏起主导作用。随着动态应力在传播过程中的快速衰减,初始围岩应力与动态应力的大小逐渐接近,并最终由初始围岩应力主导裂纹的萌生与扩展。研究结果表明,围岩应力是决定岩体裂缝发育和扩展特征的重要因素,特别是对裂缝的扩展方向有显著影响,在采用高压电脉冲致裂技术对深部岩体进行致裂时,应考虑岩体所处应力状态,科学制定致裂方案,以实现对岩体的高效致裂。

     

    Abstract: High voltage electrical pulse fracturing technology based on electrohydraulic effect is a new type of rock mass fracturing technology. This technique is characterized by its safety, high efficiency, environmental friendliness and controllable energy usage. It holds a significant potential for its application in the stress control of surrounding rock in coal mines because the complex stress conditions present in underground rock mass. To further investigate the cracking effect of the technology on hard rock mass under different surrounding rock stress conditions, the numerical simulation of high voltage electric pulse rock mass cracking was carried out on the rock sample based on the RHT damage constitutive model by LS-DYNA. The processes of damage evolution and effective stress evolution inside the rock mass were collected. The cracking characteristics and crack propagation mechanism of the rock mass were analyzed. The numerical simulation overcomes the problem that it is difficult to effectively monitor the internal rock mass during the cracking process due to the fast discharge process and large electromagnetic interference in the indoor test. The self-developed high-voltage electrical pulse rock fracturing test platform was used to carry out the high voltage electrical pulse rock fracturing test under different surrounding rock stress conditions, and the reliability of the numerical simulation results was verified by the obtained rock surface fracture characteristics. The following conclusions are obtained: ① The numerical model of LS-DYNA high voltage electric pulse rock mass fracturing is established based on the RHT constitutive model. The equivalent parameters for the numerical simulation are derived according to the energy equivalent relationship between explosive blasting and high voltage electric pulse. The reliability of these parameters is confirmed by comparing the laboratory tests results with the numerical simulation results. ② By analyzing the crack propagation on the upper surface of specimens, it reveals that the crack will deflect in the direction of the maximum compressive initial stress. Initially, the total length of the crack first decreases gradually during this process. As the angle between all cracks and the maximum initial compressive stress becomes less than 45°, the total crack length begins to increase gradually. ③ Numerical simulations demonstrate that the dynamic stress resulting from high voltage electric pulse discharge is much greater than the initial stress in the surrounding rock during the early stages of fracturing. Dynamic stress plays a leading role in rock failure in this process. As the dynamic stress quickly diminishes during propagation, the initial surrounding rock stress is gradually close to the dynamic stress and finally dominates the initiation and propagation of cracks. The results indicate that surrounding rock stress plays a crucial role in determining the development and expansion characteristics of rock mass cracks. It notably influences the direction of crack expansion. When the high voltage electric pulse fracturing technology is used to crack the deep rock mass, the stress state of the rock mass should be considered. The scientific fracturing scheme should be formulated to achieve an efficient fracturing of the rock mass. The research results provide a reliable numerical simulation method for high voltage electric pulse rock fracturing and a reference for the formulation of deep rock mass fracturing scheme.

     

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