Particle breakage of granular materials subject to explosion

Unconfined granular medium subjected to central explosion experiences transient stresses and strains which are distributed heterogeneously. The particle breakage are markedly different from the fractal fracture of granular materials under confined comminution which are typical in the quasi-static and dynamic compression experiments. The particle size distribution of shocked particles recovered from the explosive dispersal of particle shells consisting of glass spheres reveal varying breakage modes depending on the mass ratio of payload and charge, M/C. When M/C is small, the particle size distributions of blasted materials shows three regimes, and the second regime satisfies fractal distribution. The fractal dimension of the second regime ranges from 2.9 to 2.5 with increasing M/C. With M/C beyond a threshold, an increasing amount of particles remains intact, the particle size distributions of fractured materials transitions to a two-regime mode, in which the fractal dimensions are well below 2 and progressively decreases with increasing M/C. The distinct behaviors of particle breakage are a result of the compound and transient loadings due to a sequence of incident shock, unloading and reshock as revealed by grain scale investigations using FDEM.