多炮孔岩体等离子体爆破定向致裂机理研究

Research on the directional fracturing mechanism of multiborehole rock mass plasma blasting

  • 摘要: 为了研究等离子爆破技术结合切缝管和预切槽技术的定向致裂效果,开展等离子体电脉冲定向致裂试验,探究不同切缝管切缝形状和不同预切槽间距下等离子体爆破定向致裂机理和定向断裂效果,对比分析不同定向形式作用下等离子体爆破岩石定向断裂贯通效果. 结果表明,与正楔形切缝管和平切形切缝管相比,切缝管岩石试件中倒楔形结构中产生的应力峰值最大,聚能效果最显著,其定向贯通岩石效果更显著. 预切槽岩石的电爆聚能致裂效果随着钻孔切槽间距的增加而减小. 切槽间距为40 mm时,预切槽岩石试件等离子体电脉冲的聚能效果优异,产生定向裂纹的效果明显优于切槽间距为50 mm和60 mm的预切槽岩石试件. 同时,预切槽定向形式的等离子体爆破定向致裂效果相对于切缝管定向致裂效果更为显著.

     

    Abstract: The study examines the directional fracturing effects of plasma blasting technology when combined with slit tube and precut groove technologies. Plasma electric pulse directional fracturing tests were carried out using two groups of test variables. The aim was to explore how different slit tube shapes and precut groove spacings affect the mechanism of directional rock fracturing under various configurations of plasma blasting. In the first set of experiments, results indicated that the embedded inverted wedge-shaped slip guides crack initiation, expansion, and extension along the intended rupture surface direction compared to both positive wedge-shaped slit pipe and flat cut slit pipe. The shape of the cut slit significantly affects the directional fracturing effect during rock electrobursting. The inverted wedge-shaped slit pipe exhibits a cross-sectional area that gradually decreases from the inside to the outside, resulting in strong energy convergence during the plasma blasting process. This configuration generates maximum peak stress on both sides of the slit, ensuring a higher degree of flatness on the inner surface of the rock specimen. Consequently, it produces the fewest secondary cracks and achieves more effective directional penetration through the rock. The second group of experiments revealed that prefabricated grooved rock specimens use precut grooves to steer the direction of crack expansion and rupture surface formation. As the spacing among these grooves increases, the effectiveness of the electro-explosive fusion fracturing gradually diminishes, leading to greater deviation from the expected crack direction. When the precut slot spacing is small, the shock waves from the electro-explosive events are closer together, overlapping to form a combined shock wave. At a 40-mm slot spacing, the precut groove rock specimens exhibited optimal energy convergence from plasma electric pulses, forming a coupling surface along the precut groove line. This configuration enhances stress intensity at the rock crack tip, resulting in more precise directional cracks compared to spacing of 50 mm and 60 mm. At the same time, the directional fracturing effect of plasma blasting is more pronounced in precut groove orientations than that in slit pipe configurations, offering excellent penetration along the intended path.

     

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