起爆方式对间隔装药应力场分布及裂纹扩展的影响

通过模型实验研究了不同起爆方式对空气间隔装药炮孔两侧损伤分布的影响规律，借助数字图像相关实验系统，获取了全场应变场演化过程及空气段应变衰减规律，同时借助透射式焦散线实验系统，探究了起爆方式对预制裂纹动态断裂行为的影响.实验结果表明：柱状药包炮孔两侧产生的损伤范围具有显著的分形特征.采用外侧起爆时，空气段中心两侧均产生损伤，而采用其他起爆方式时，空气段均未出现损伤.不同起爆方式对空气段应变场径向压应变的影响主要体现在应变大小、衰减速度两个方面，对轴向拉应变的影响主要体现在时效性、衰减速度两个方面.不同起爆方式下预制裂纹端部断裂行为差别较大.采用内侧起爆、外侧起爆时，裂纹均为水平扩展，呈现典型Ⅰ型裂纹，裂纹起裂主要由拉伸破坏引起，异侧起爆时裂纹起裂为Ⅰ-Ⅱ混合型，具体表现为拉-剪破坏.基于数值模拟软件LS-DYNA，解释了预制裂纹端部起裂成因，得到了孔壁处应力场分布规律，不同起爆方式对炮孔轴向孔壁处压力分布影响显著，装药段主要体现在压力峰值位置和压力分布形态两个方面，空气段主要体现在压力峰值大小和压力分布形态两个方面.

Effect of the detonation method on the stress field distribution and crack propagation of spacer charge blasting

In this study, a numerical simulation is used to study the effect of initiation methods on the damage distribution on both sides of an air-spaced charge blasthole using lead azide as the explosive and polymethyl methacrylate as the experimental material. The digital image correlation system determines the evolution of the global strain field and the strain attenuation pattern of the air section, and the dynamic caustics experimental system investigates the effect of detonation methods on the dynamic fracture behavior of the precrack. The experimental results show that the damage induced on both sides of the cylindrical charge blasthole has significant fractal properties. The damage degree corresponding to each initiation point of the charge section is the smallest, and the damage degree gradually increases along the detonation path. When it approaches the noninitiating end, the damage degree reduces further due to a decrease in the energy accumulation rate and a portion of the energy dissipation. When the outer detonation method is employed, both sides of the central air section are damaged, but not when the other detonation methods are used. The effect of different initiation methods on the radial compressive strain of the air segment strain field is mostly reflected in the strain size and strain decay rate, whereas the effect on the axial tensile strain is primarily reflected dynamically and in the decay rate. The attenuation coefficient of the strain field is the greatest when the outer detonation is initiated, regardless of whether the strain is radial or axial. The fracture behavior of the precrack end varies considerably depending on the detonation method. When both the inner and outer detonations are used, the crack exhibits a typical I type generated by tensile failure. When antarafacial detonation is used, the crack initiation is mixed I–II, and the specific performance is tensile-shear destruction. The origin of the crack initiation at the end of the precrack is described using LS-DYNA numerical simulation software, and the distribution pattern of the stress field at the blasthole wall is derived. The pressure distribution along the axial hole wall of the blasthole is considerably affected by different detonation methods. The charge section is mainly reflected in the position of the pressure peak and the pressure distribution shape, whereas the air section is primarily reflected in the size of the pressure peak and the pressure distribution shape.