不耦合装药下岩石爆破块体尺寸的分布特征

Size distribution characteristics of blast-induced rock fragmentation under decoupled charge structures

通过不同装药结构下立方体红砂岩小型爆破实验,分析了岩石的损伤程度和破坏模式,同时引入三参数极值分布函数量化岩石爆破块体尺寸分布特征。此外,根据岩样R1的爆破实验结果进行了有限元数值模型验证,基于验证的模型展开了岩石单孔爆破损伤破裂行为的模拟,讨论了径向、轴向不耦合系数和耦合介质对岩石破碎效果的影响。结果表明,三参数极值分布函数可以较好地表征岩石爆破后破碎块体尺寸分布特征,块体平均尺寸随着不耦合系数的减小呈线性降低趋势,且破碎块度趋于均匀。通过比较不同耦合介质装药时岩石内部的能量分布特征和破坏体积发现,水作为耦合介质时,爆炸能量的传递效率最高,其次分别是湿砂和干砂,空气的能量传递效率最低。结合等效波阻法计算的理论应力透射系数可以很好地反映不耦合装药时岩石的破碎程度。

Decoupled charge structure is widely used in contour blasting for rock excavation engineering,and its efficacy in rock breaking is tied intricately to both the decoupling ratio and the transfer features of explosion energy.In this study,the analysis delves into the damage degree and failure patterns of cubic red sandstone samples through two groups of lab-scale blasting tests utilizing various charging modes.To precisely quantify the features of rock fragmentation size distribution(FSD)induced by blasting load,a three-parameter generalized extreme value(GEV)function was introduced.In addition,a threedimensional finite element model was developed in ANSYS software.The numerical model was calibrated based on the tested results of sample R1 by comparing the fracture networks and FSD curves.This validated model was then deployed to model the rock fracture behavior under decoupled charge blasting,and the evolution of blasting cracks and explosion pressure inside the rock sample was reproduced.Moreover,the effects of axial and radial decoupled ratios and the choice of coupling medium on the rock fragmentation and fracture patterns were discussed.The results showed that the three-parameter GEV function can better characterize the rock fragmentation features resulting from blasting.Notably,the average size of the fragment decreases linearly with the decrease of the decoupling ratio,and the degree of fragmentation tends to be uniform.By comparing the energy distribution and damage levels of rock when using different coupling mediums,it was found that water as the coupling medium exhibits the highest efficiency in energy transfer,followed by wet sand and dry sand,and air has the lowest energy transfer efficiency.Furthermore,the theoretical stress transmission coefficient calculated by the equivalent wave impedance method can well reflect the rock fragmentation features and serve as a valuable reference for rock blasting in decoupled charge.