Improving the DDA Solution Time by Modifying the Contact Enforcement Technique

M.S. Khan, A. Riahi, J.H. Curran

In the proceedings of: GEO2011: 64th Canadian Geotechnical Conference, 14th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 5th Pan-American Conference on Teaching and Learning of Geotechnical Engineering

Session: Mining and Rock Mechanics

ABSTRACT: This paper will focus on the efficiency of Discontinuous Deformation Analysis (DDA) applied to jointed rock problems. DDA uses an implicit time-integration scheme to solve the governing equations of motion through time. It therefore requires forming global system of equations. In recent studies, the authors have shown that although theoretically there is no restriction on DDA time-step size, DDA-Shi is in fact slower than methods that utilize an explicit time integration scheme. The observed slowness in the DDA solution of real-scale geotechnical problems is caused by the combination of the highly nonlinear nature of contact problems and the size of the global system of equations in implicit time integration techniques. This paper will focus on improving the computational efficiency of DDA-Shi by adopting a concept similar to the soft contact approach. It will be shown that by removing the no-penetration constraint of the contact penalty enforcement in DDA-Shi, the solution time decreases significantly. The conclusions are verified in examples that examine the stability of slopes in jointed rock masses.

RÉSUMÉ: Cet article mettra l'accent sur l'efficacité de l'analyse de la déformation discontinue (ADD) appliqués aux problèmes des gouvernent le mouvement à travers le temps. Il faut donc former un système global des équations. Dans des études récentes, il a été démontré que même si théoriquement il n'y a aucune restriction sur la taille du temps--Shi est effectivement plus lente que les méthodes qui utilisent un système d'intégration temporelle explicit. La combinaison de la nature des problèmes de contact, qui sont extrêmement non-linéaire, et de la taille du système global des équations dans les techniques d'intégration temporelle implicite. Cet article se concentrera sur l'amélioration de -Shi en prennant un concept similaire à l'approche du contact souple. Il sera démontré que, en supprimant la contrainte de non-pénétration de l'application des peines du contact, le temps de la solution diminue de manière considérable. Les conclusions sont vérifiées dans les exemples qui examinent la stabilité des pentes dans les masses de roches démontables.

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