高瓦斯低渗煤层控制孔与定向控制爆破复合作用增透试验研究

Experimental study on permeability enhancement by combined action of control hole and directional control blasting in high gas and low permeability coal seam

针对高瓦斯低渗煤层爆破增透时爆破裂隙不能较好的沿煤层方向扩展,爆破能量利用率低的问题,进行控制孔与定向控制爆破复合作用增透试验研究。根据爆炸应力波的传播规律,建立控制孔辅助作用下爆炸应力波传播的力学模型,将爆破后4组不同孔径控制孔与1组无控制孔的裂纹起裂及应力发展规律进行对比分析,得出爆生裂纹的扩展规律以及应力峰值的涨幅关系。利用自主搭建的爆破试验平台进行爆破相似模拟试验,结果表明,在裂纹扩展方面,当控制孔孔径过小,控制孔对裂纹导向作用较弱,爆破孔和控制孔之间平行于煤层裂纹不明显;随着孔径增大,控制孔对裂纹导向作用加强,双孔之间形成平直的贯通爆生裂纹,定向作用较为明显。应力方面,控制孔迎爆侧应力峰值随着孔径增大而增大,最大涨幅为40.4%;在控制孔背爆侧随着孔径增大应力峰值呈先增加后减小的动态趋势,即周围应力场随着孔径的增大会出现一个最大应力场。研究成果运用于高瓦斯低渗煤层定向控制爆破中,可以有效提高爆破能量利用率和煤层透气性。

Aiming at the problem of the low utilization of blasting energy due to that the burst gap cannot expand well in the direction of the coal seam during the blasting increasing permeability of high gas low permeability coal seam,the experimental study of the composite effect of control hole and directional control blasting is carried out.According to the propagation law of explosion stress wave,the mechanical model of explosion stress wave propagation under the auxiliary action of control hole is established.The four groups of control holes with different apertures after blasting are compared and analyzed with the crack initiation and stress development law of one group without control holes,and the propagation law of bursting cracks and the amount of increase of stress peak are obtained.The self-built blasting test platform is used to carry out blasting similarity simulation test.The results show that in terms of crack propagation,when the control hole diameter is too small,the control hole has a weak effect on crack guidance,and the crack parallel to the coal seam between the blasting hole and the control hole is not obvious.With the increase of the aperture,the control hole's effect on the crack orientation is strengthened,a straight connecting burst crack is formed between the two holes,and the orientation effect is more obvious.In terms of stress,the stress peak on the blasting side of the control hole increases with the augment of the aperture,and the maximum percentage of increase is 40.4%.On the back of blasting side of the control hole,the stress peak increases first and then decreases as the aperture increases,that is,the surrounding stress field will have a maximum stress field as the aperture increases.The research results are applied to the directional controlled blasting of high gas and low permeability coal seams,which can effectively improve the blasting energy utilization rate and permeability of coal seam.