OFFICIAL THEORETICAL BASIS OF NUMERICAL MODELING WITH ELFEN PROGRAM FEA MODEL To generate fragmentation in rock, it is necessary to work with an MBM (Mechanistic Blasting Model), which is an explicit model where the codes of finite and discrete elements are coupled. This code has evolved from the work of Munjiza (Munjiza, 1992). The rock mass is generated by a mesh of first-order tetrahedral finite elements since these can be easily adapted to any geometry and have less computational cost for calculations. If we consider that the CFD and DEM models work in tandem, this type of triangular element is the most accepted to reduce calculation times. The boundary conditions of the system are obtained from the CFD model, which are entered into the program as a variable load over time. This produces a pressure on the elements that form the wall of the study blasthole. The model for calculating fracture is based on a simplified plastic model of Rankine (1857), where each element is reviewed for each timestep. A fracture can occur if the stress of the element exceeds the tensile limit and then decays to zero. =− 2 2 ඥ (2) Where: σt = Tractive effort. Gf = It is the coefficient of energy release per fracture. Ai = It is the area of the element. The fracture energy (Equation 5) is the one that governs once the maximum tensile stress has been reached, that is, when the material begins its plastic deformation. Illustration 2; Fracture based on the Rankine model.
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