不同耦合介质爆破裂纹动态扩展特性研究

STUDY ON DYNAMIC PROPAGATION CHARACTERISTICS OF BLASTING CRACKS IN DIFFERENT COUPLING MEDIA

不耦合装药结构能有效改善爆破效果。为探究不同耦合介质对爆破效果的影响,利用透射式数字激光焦散线实验系统,对有机玻璃板(polymethyl methacrylate,PMMA)试件开展水、空气、沙土3种耦合介质的不耦合爆破试验,研究不同耦合介质爆后裂纹形貌,计算裂纹分形维数,定量评价岩石破坏程度。分析裂纹扩展速度与动态应力强度因子变化规律,对比不同耦合介质下爆生裂纹的动态力学行为。结合数值模拟进行辅助分析,解释不同耦合介质对数值模拟中爆破损伤范围、孔壁压力时间曲线和岩石模型的总能量曲线的影响规律。结果表明:水耦合爆后裂纹分形维数最大,炮孔周围裂纹数量众多,主裂纹扩展长度最大,爆破效果最佳。沙土耦合爆破需要更多的能量使裂尖起裂,其动态应力强度因子最大。模拟得到的损伤云图与实验结果一致,水耦合损伤范围最大,空气耦合次之,沙土耦合损伤范围集中在炮孔周围。而孔壁压力时程曲线、能量时程曲线则验证爆破实验结果,表明水耦合爆破能更好地利用爆炸能量,提高试件的破坏效果。

The uncoupled charging structure can effectively improve the blasting effect.In order to explore the impact of different coupling media on the blasting effect,the transmission digital laser caustics experimental system is used to carry out the uncoupled blasting test of polymethyl methacrylate(PMMA)specimens in three coupling media,i.e.,water,air and sand,to study the crack morphology after blasting in different coupling media,calculate the fractal dimension of the crack,and quantitatively evaluate the degree of rock damage.The dynamic mechanical behavior of crack initiation under different coupling media is compared by analyzing the change law of crack growth speed and dynamic stress intensity factor.Through combining numerical simulation for auxiliary analysis,it explains the influence of different coupling media on the range of blasting damage,the time curve of hole wall pressure,and the total energy curve of the rock model in numerical simulation.Results show that after water coupling explosion,the crack analysis dimension is the largest,and there are many cracks around the blast hole.Mhe main crack propagation length is the largest,and the blasting effect is the best.Sand soil coupling blasting requires more energy to make the crack tip crack,and its dynamic stress intensity factor is the largest.The simulated damage contour is consistent with the experimental results.The water coupling damage range is the largest,followed by air coupling.The sand soil coupling damage range is concentrated around the borehole.The time history curves of hole wall pressure and energy validate the results of blasting experiments,indicating that water coupled blasting can better utilize blasting energy and improve the failure effect of the specimen.