双孔聚能爆破煤层裂隙扩展贯通机理

Crack propagation and coalescence mechanism of double-hole cumulative blasting in coal seam

针对双孔聚能爆破孔间煤层裂隙扩展贯通问题,基于对双孔爆破应力波叠加效应的分析,建立双孔聚能爆破数值分析模型,研究双孔同时起爆时应力波的传播特征、煤体的应力状态、煤体裂隙扩展贯通规律以及应力波叠加效应对裂隙扩展的影响.结果表明,应力波叠加效应致使两爆破孔中间截面上部分区域及其邻域内形成均压区,迫使部分径向裂隙转向,主导爆生裂隙空白带的形成;两爆破孔间的定向裂隙相互贯通后,爆生气体相互作用促进贯通区裂隙的扩展并贯穿空白带.同时,结合煤层深孔聚能爆破现场试验发现,在两爆破孔外侧,应力波叠加效应促进裂隙的扩展,该作用随着远离爆破孔呈先增加后减小之势;在两爆破孔之间,应力波叠加效应抑制部分区域裂隙的扩展,致使两爆破孔之间不同位置处煤层增透效果有起伏变化.

This paper focuses on the radius of coal failure zones under cumulative blasting with shaped charge.Based on the analysis of the mutual superposition effect of the explosion stress waves during the simultaneous detonation of two blastholes,a numerical analysis model of the double-hole cumulative blasting with linear shaped charge was established.Additionally,the propagation characteristics of the stress wave during the simultaneous detonation of two blastholes,stress state of the coal body,mechanism of coal crack propagation and coalescence,and influence of the stress wave superposition effect on crack propagation were evaluated.Results show that the stress wave superposition effect induces the formation of a pressure equalization zone in the partial region of the middle section of the two blastholes and its adjacent regions.This occurrence forces the radial cracks of the two blastholes to turn,and they cannot connect with each other,leading to the formation of a gap blank zone between the two blastholes.After the directional cracks generated under cumulative blasting load coalesce,the collision of the explosive gases produced from the two blastholes further promotes the expansion of the cracks in the directional crack coalescence zone and eventually penetrates the gap blank zone.Field test results of deep-hole cumulative blasting in coal seams show that the explosion stress waves from the blastholes in the opposite side promotes the propagation of the blasting-induced crack on the left or right side of the two blastholes.This propagation first increases and then decreases as it moves away from the blasthole.Between the two blastholes,the stress wave superposition effect from the two blastholes inhibits the propagation of the cracks in some areas,resulting in a W-like fluctuation in the degree of improvement of the gas drainage effect at different positions in the area between the two blastholes.