深孔聚能爆破起爆位置对煤层致裂增透的影响

Effect of detonating position of deep-hole cumulative blasting on coal seam cracking and permeability enhancement

  • 摘要: 针对深孔聚能爆破起爆位置对煤层致裂增透的作用,在分析了不同起爆位置的爆轰波传播、爆炸应力场分布特征的基础上,采用数值模拟的方法探讨了不同起爆位置对聚能流形成和煤体裂隙发育特征的影响,并基于平煤股份十矿己组煤层瓦斯地质条件,进行了煤层深孔聚能爆破现场试验研究。结果表明:起爆位置通过控制聚能药包中爆轰波及应力波传播方式,对煤岩爆生裂隙发育产生影响。爆轰波碰撞以及应力波叠加效应是导致爆生裂隙沿药包轴线分布不均的重要原因。在不同位置起爆的深孔聚能爆破作用使裂隙发育表现出不同的特征:在一端起爆条件下,爆破孔周围产生的应力场沿爆轰波传播方向逐渐增强,爆生裂隙范围由起爆端至药包另一端呈逐渐增大的趋势;在两端齐爆条件下,爆轰波碰撞形成的爆轰超压驱动聚能槽相互碰撞产生动能更大的聚能流,与爆炸应力波的叠加共同作用,扩大了局部裂隙范围;在三点齐爆条件下,爆轰波在药包三等分点处发生碰撞产生超压以及各起爆点产生的锥面应力波互相叠加,导致在药包三等分点附近形成更大范围裂隙。随着起爆点增加,在起爆点之间的装药长度相应缩短,减弱了锥面应力波之间的叠加效应,缩小了爆轰波碰撞点处爆生裂隙发育范围与其他位置爆生裂隙范围的差距,使爆生裂隙沿药包轴线分布更均匀。

     

    Abstract: This paper is concerned with the effect of detonating position of deep-hole cumulative blasting on coal seam cracking and permeability enhancement.Based on the analysis of the propagation of detonation wave and the distribution of explosion stress field, the formation of cumulative energy flow and the development of coal crack under the conditions of different detonating positions were studied by numerical simulation.Then, according to the gas geological conditions of the coal seam in the No.10 mine of Pingdingshan, the field tests of deep-hole cumulative blasting in coal seam were carried out.The results indicate that the initiation position have an influence on the development of coal rock blasting cracks, by controlling the propagation mode of detonation wave and stress wave in cumulative charge.Detonation wave collision and stress wave superposition effect are important reasons for the uneven distribution of explosive cracks along the axis of charge.The effect of deep-hole cumulative blasting initiated at different positions makes the fracture development show different characteristics.When the charge is detonated at one end, the stress field around the blasting hole increases gradually along the propagation direction of detonation wave, and the range of detonation cracks increases gradually from the initiation end to the other end of the charge.Besides, under the condition of simultaneous detonation at both ends, the detonation overpressure formed by detonation wave collision drives the energy accumulation grooves to collide with each other to produce cumulative flow with greater kinetic energy, which acts together with the superposition of explosion stress waves to expand the range of local cracks.Furthermore, under the condition of three-point simultaneous detonation, the detonation wave collision and conical stress wave are superimposed near the trisection point of the charge, resulting in the formation of a wider range of cracks.With the increase of the initiation point, the charge length between the initiation points is shortened accordingly, which weakens the superposition effect between conical stress waves, reduces the gap between the development range of explosive cracks at the impact point of detonation wave and that at other positions, and makes the explosive cracks distributed more evenly along the axis of charge.

     

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