煤层深孔聚能爆破动力效应分析与应用

Dynamic effects of deep-hole cumulative blasting in coal seam and its application

为研究煤层深孔聚能爆破致裂增透机理,构建聚能爆破分析模型,运用理论分析与数值模拟相结合的方法探讨聚能爆破时聚能射流的成型机理、爆炸应力波的传播特点、煤体力学特征和裂隙扩展机理.结果表明：聚能槽集聚爆轰能量形成聚能射流并产生聚能效应,聚能效应显著改变了爆炸应力波的传播特性和煤体的力学性质,在聚能方向煤体所受压应力峰值是非聚能方向的1.10~1.29倍,有效地促进了裂隙的扩展;且主聚能方向煤体所受压应力峰值由次聚能方向的0.85倍增大到1.06倍,放缓了煤体所受应力的衰减速度.此外,煤层深孔聚能爆破工程应用实验表明,聚能爆破后抽采孔平均瓦斯含量是聚能爆破前的1.58倍,有效地提高了煤层透气性和瓦斯抽采率.

A model of cumulative blasting was established to study the mechanism of crack propagation and permeability increasing under cumulative blasting in a coal seam. The forming mechanism of shaped charge jet, the propagation characteristics of stress wave and detonation wave, the stress distribution characteristics of coal elements, and the mechanism of crack extension under cumula- tive blasting were investigated by theoretical analysis and numerical simulation. It is found that the propagation characteristics of deto- nation wave promote the forming of cumulative jet, and change the propagation characteristics of stress wave and the stress distribution characteristics of coal elements significantly. The stress peak values of coal in the major and minor cumulative directions are 1.10- 1.29 times that of coal in the non-cumulative direction, and the stress peak value of coal in the major cumulative direction increases from 0. 85 times that of coal in the minor cumulative direction to 1.06 times in the range of blasting effect, slowing down the attenuation rate of the stress peak value of coal and increasing the crack propagation velocity. Besides, field experimental results of cumulative blasting in a coal seam indicate that the average concentration of extracted gas after blasting is 1.58 times that before blasting, and cumulative blasting can promote crack propagation effectively.