Abstract: The particle flow code in two dimensions (PFC2D) software was used to construct a numerical model for analyzing the effects of dynamic impact loads on coral sands with random internal pore distributions. The evolution law of particle breakage was described combining of the force chain distributions, crack development and fragmentation patterns. The results indicate that the single-grain dynamic breakage strength in the coral sand follows the Weibull distribution pattern. Under impact loads, the force chains of a coral sand particle will first appear around the internal pore-end and loading-end. Most of the mesoscopic cracks form along these force chains, and the force chains will weaken around cracks. The cracks often appear in the tensile stress concentration zones and the primary crack will grow along the loading axis. The secondary cracks, which are formed by the crack deflection towards the internal pores, will extend towards the edges of the specimen and merge with adjacent cracks to penetrate the specimen, breaking it into multiple breakages. At higher loading rates, more cracks initiate from the internal pores and increase at a much faster rate. Crack penetration is also more common. 

Key words: coral sand, particle breakage, particle flow code, internal pores, loading rate