EXTENSIONS OF DISCONTINUOUS DEFORMATION ANALYSIS FOR JOINTED ROCK MASSES

Beginning with the original work of Shi [Discontinuous deformation ana lysis: a new numerical method for the statics and dynamics of block sy stems. Ph.D. thesis, University of California, Berkeley, (1988)], call ed the Discontinuous Deformation Analysis (DDA) method, a number of ex tensions to the method have been explored. The extensions consist of i mproving the contact algorithm, adding block fracturing and sub-blocki ng capabilities. Contacts between blocks have been modeled using an Au gmented Lagrangian Method instead of the penalty method originally pro posed by Shi. This allows block-to-block contacts to be enforced more precisely and block contact forces to be determined more accurately. A sub-blocking capability has been developed, whereby blocks are discre tized into sub-blocks. The continuity, of the sub-block contacts is pr eserved and the variation of stresses in each large block can be deter mined. The sub-blocking capability is none using a consistent formulat ion in which the same methodology is used for the sub-blocks as the or iginal large blocks. This is different from other discrete block metho ds that imbed finite difference zones or finite elements inside larger blocks. Finally, two block fracturing algorithms have been implemente d in the DDA method. Using a three-parameter (cohesion, friction, tens ile strength) Mohr-Coulomb criterion, one algorithm allows intact rock s to be broken into smaller blocks. Fracturing can be irt shear or ten sion. The second algorithm allows fractures to propagate in the sub-bl ocks either in Mode I (tensile fracturing) or Mode II (shear fracturin g). All three extensions have been implemented into the original DDA p rogram of Shi. With the three extensions, the DDA method is more appli cable to a greater range of rock mechanics problems and other engineer ing problems involving blocky systems. Examples of application of the method, for plane stress condition, are presented with regard to rock fall, slope stability and underground excavation problems. Copyright ( C) 1996 Elsevier Science Ltd