应力波形对岩石爆生裂纹扩展机制影响的数值模拟

Effect of stress waveform on the rock blasting crack propagation mechanism using numerical simulation

运用RFPA^(3D)动力分析软件模拟了冲击动力作用下含预制裂纹岩石的裂纹扩展过程,探究了应力波峰值、能量、上升及下降速率对岩石裂纹扩展过程的影响.研究表明动载下岩石裂纹扩展形态受应力波上升速率影响,应力波上升速率越快,孔周边岩石越破碎;应力波能量影响裂纹扩展长度,能量越大裂纹扩展越长,而相同能量条件下,应力波上升速率越小,裂纹扩展距离越远,但孔边破碎程度越弱;上升速率和应力波上升沿能量共同影响着炮孔粉碎区半径.数值模拟结果很好地揭示了不同应力波峰值、能量与上升/下降速率对岩石的破碎机制,在实际爆破作业中可以通过水炮泥封口或者采用空气柱间隔装药结构来延长应力波作用时间,以达到扩大爆破影响范围的目的,而通过选取合适类型与配比的炸药来提升应力波上升速率从而增强孔边破碎效果.

The type,proportion,and charging method of explosives produce different stress waveforms,which greatly affect rock crack propagation.Because of the complex interaction law between waveform parameters such as the peak value,wavelength,energy,and rise or fall rate,and the limited physical and mechanical test conditions,quantitatively controlling waveform parameters in a blasting test is difficult.Numerical simulation has advantages in revealing the influence law of the stress wave.In this paper,RFPA^(3D) dynamic analysis software was used to simulate the crack propagation in a rock with a prefabricated crack under impact loads,and the effects of the stress wave peak value,energy,rise rate,and fall rate of the stress wave on the rock crack propagation process were investigated.Results show that the rock crack propagation pattern under dynamic loads was affected by the rise rate of the stress wave.The faster the stress wave rose,the more breakages occurred around the hole.For the crack propagation length,the crack grew longer with the increase in the stress wave energy.When the stress wave energy was constant,the crack grew farther with the decrease in the rise rate,but the broken degree around the hole was decreased.The rise rate and the energy of the rising edge of the stress wave affected the radius of the comminution zone.Numerical simulation results revealed the rock crushing mechanism of different stress wave peak values,energies,and rise or fall rates.In a practical engineering blasting operation,to expand the impact range of blasting,extending the action time using a water cannon mud seal or an air column interval charge structure was suggested.In addition,the appropriate type and proportion of explosives were also selected to increase the stress wave’s rise rate to improve the effect of hole edge crushing.