放电电压对组孔脉冲破岩裂纹分布与破裂程度影响研究

Effect of discharge voltage on crack distribution and fracture extent in multi-hole pulsed discharge rock fragmentation

  • 摘要: 为了深入探究放电电压对组孔脉冲破岩裂纹分布与破裂程度的影响,以红砂岩为研究对象,在50~90 kV电压范围内,以10 kV为间隔开展5组组孔脉冲放电破岩对比实验。通过对试件切割染色处理并结合裂纹图像识别技术,定量表征了岩石损伤面的裂纹密度、分形维数和损伤变量。采用有限元分析软件LS-DYNA进行数值模拟,分析了二次放电过程中岩石内部裂纹发育过程、有效应力峰值随距离的变化规律和不同放电电压下第二次放电对第一次放电产生裂纹的影响。研究结果表明:当放电电压从50 kV提升到70 kV时,裂纹密度增加54.5 %,分形维数增大6.4 %,损伤值上升67 %;而放电电压从70 kV进一步提升时,3项指标的走势并没有继续上升,而是趋于稳定;在较高的放电电压下,第二次放电会引发第一次放电产生损伤的二次发育。

     

    Abstract: This study investigates the effect of discharge voltage on fracture distribution and fragmentation extent in multi-hole pulsed discharge rock fragmentation. Comparative experiments were conducted on red sandstone specimens across 5 voltage levels ranging from 50 kV to 90 kV (in 10 kV increments). Rock damage surfaces were quantitatively characterized in terms of crack density, fractal dimension and damage variable through specimen cutting, staining and crack image processing. Numerical simulations were conducted using the LS-DYNA finite element analysis software to analyze the crack propagation process within the rock mass during dual discharges and the effect of the second discharge (at varying voltages) on pre-existing cracks induced by the first discharge. Results indicate that increasing the discharge voltage from 50 kV to 70 kV led to a 54.5 % increase in crack density, a 6.4 % rise in fractal dimension, and a 67 % increase in the damage variable. However, further voltage increases beyond 70 kV resulted in stabilization of these 3 metrics rather than continued growth. At higher discharge voltages, the second discharge triggered secondary propagation of damage initially caused by the first discharge.

     

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