Stability analysis of concrete dam foundations following a hybrid discrete element/finite element approach

Abstract

In concrete dam foundations, failure mechanisms are primarily influenced by natural rock discontinuities, the dam-foundation interface, or weaker strata. Instability can manifest beneath the dam, within the abutments, or along adjacent slopes. For arch dam foundations, particular attention is required for failure scenarios involving sliding along weaker surfaces in areas where the arches are supported (along the valley sides and abutments), as well as issues related to seepage at the valley bottom, that may lead to the discontinuities erosion. Sophisticated analyses employ discrete element models, which capture well the discontinuous nature of rock and can incorporate fluid flow through these discontinuities. In stability analyses of concrete dam foundations, interface models whether based on discrete element or finite element techniques typically use planar joint formulations, such as point-to-point, point-to-surface, and edge-to-edge contacts. This paper introduces a new hybrid discrete element/finite element approach. When large displacement may occur, the rock blocks outer surfaces are discretized with spherical particles, allowing interactions to be modelled through particle-to-triangular surface interactions which are known to be computationally robust. Whenever possible, the contact interaction is defined in small displacements using finite element joint elements. A simplified gravity dam equilibrium example is presented to validate the proposed hybrid model. Stability analysis of an idealized arch dam foundation is also performed. The presented results are shown to closely match those obtained with a more complex polyhedral-based discrete element model.