Abstract：The particle flow codeis is used to analyze crack propagation rules and mechanisms of holed-flattened Brazilian disc with different aperture. The results show that there is a certain difference in the fracture mode of Brazil disc specimen with different center hole diameter. Regardless of the size of the hole,the main cracksare initiated from both ends of the hole in the loading direction and extend along the loading direction. If the center aperture is small,the secondary cracks will be initiated from the loading point and connected to the main cracks,which lead to the rupture of the disc specimen in half. If the center aperture is large,the secondary cracks will be initiated from the side of the loading point and extend to the center hole,which divide the disc specimen into four parts. The spliting process of holed-flattened Brazilian disc can be divided into fourstages: elastic deformation,initiation and stable propagation of the main cracks,unstable failure of the main cracks,unstable failure of the secondary cracks. From the point of view of stress field,tensile stress concentration area continually transfers and forms new micro tensile cracks during the spliting process. The initiation,propagation and coal escence of many micro tensile cracks form the macroscopic fracture. From the point of view of energy,the continuous strain energy accumulates in the initial loading. Then strain energy releases sharply and dissipative energy increases rapidly after peak strength.

Keyword：Brazilian test;holed-flattened Brazilian disc;crack propagation;particle flow code(PFC);