Block fracturing analysis using nodal-based discontinuous deformationanalysis with double minimization procedure

Nodal-based Discontinuous Deformation Analysis (NDDA) can be regarded as a hybrid method of Finite Element Method (FEM) and Discontinuous Deformation Analysis (DDA), of which its model couples DDA's unique block kinematics with the well-developed finite element mesh. In the NDDA, nodal displacements are chosen as the basic unknowns, and the degrees of freedom are then dependent on the number of nodes. After the combination, DDA's block kinematics remains unchanged and the stress fields of blocks are refined. What makes NDDA a more promising method is the ability of modeling crack propagation problem. In the NDDA program, each mesh line is regarded as a potential crack by allowing tensile and shear fracture inside an intact block when certain criteria are satisfied, and the NDDA program is able to transform material from continuum into discontinuum. To obtain a more realistic fracture model, this paper introduces a double-minimization method presented by D.Ciancio to evaluate the stresses transmitted across mesh lines in NDDA, at the same time, adopts a suitable crack inserting procedure strictly based on the time sequence. The numerical example presented aims to verify the accuracy of the method and the results show that the proposed method generates a realistic fracture pattern.