For the purpose of studying the mechanical impact on dynamic crack propagation mechanisms of water-coupling charge under directional fracture blasting,the caustic theory and digital laser dynamic caustic experimental system were employed.The water-coupling and air-coupling directional blasting caustic experiments were performed using single-borehole PMMA specimens with pre-existing cracks un-der three different decoupling coefficients(1.25,1.67,2).Key parameter evolutions with time inclu-ding the fractal box dimensions D,dynamic stress intensity factors KdI and crack propagation velocities v of specimens with water-coupling charges were compared and analyzed.The results showed that:com-pared with air-coupling specimens,specimens with water-coupling charged generate less wing cracks and the directional cracking effect were better;KdI and v of developing cracks with water-coupling charged fluctuate gentler and more stable than those with air-coupling charges do,which indicated such charge mode provided steady and consecutive energy to crack propagation during post cracking periods;decou-pling coefficients had positive effects on dynamic initiation toughness KdIc,and the crack was more prone to initiating when decoupling coefficient is relatively low.
维普
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