Development of discontinuous deformation analysis with displacement-dependent interface shear strength

Discontinuous deformation analysis (DDA) has been widely applied in simulations of discontinuous blocky systems. The behavior of a discontinuous blocky system is mainly governed by the strength of the interface joints. The Mohr–Coulomb joint failure criterion, adopted in the original DDA, is examined through a classic case of a single block on an inclined plane. It shows that when interface cohesion exists, the block may be unstable even if the interface strength is greater than the theoretical strength required for critical stability, as the cohesion has been improperly removed. Adopting relative displacement between contacted blocks as the criterion for the removal of cohesion will provide more accurate results. The development of DDA with displacement-dependent interface shear strength is presented in this paper. To implement and illustrate the modified algorithm, two examples of progressive landslide failure simulations are performed. Both systems exhibit a two-stage failure pattern: a relatively slow, downward progressive failure stage followed by a rapid, massive run out failure stage.