Application of hydraulic fracturing for preconditioning of hard rock in underground caving mines has been demonstrated to be an effective means to induce and promote cave growth. Using Itasca's particle flow code PFC2D, a real scale numerical test environment has been developed to assess the effect of preconditioning by hydraulic fracturing on primary fragmentation. The environment makes use of the synthetic rock mass (SRM) method to simulate the mechanical behavior of hard rock mass. This technique uses the bonded particle model for rock to represent intact material and the smooth-joint contact model (SJM) to represent the in situ discontinuities and the induced hydraulic fractures. A series of hypothetic scenarios of veined hard rock mass (stockwork) based on El Teniente mine has been simulated using this environment. The results emphasize the impact of preconditioning on primary fragmentation in veined hard rocks.