A Progressive Approach to Account for Large-Scale Roughness of Concrete–Rock Interface in Practical Stability Analyses for Dam Safety Evaluation

Abstract

This paper proposes a progressive approach to assess the properties of large-scale roughness at dam–rock interfaces and the implementation of their effects into practical dam stability analyses. The analysis steps, ranked per increasing degree of complexity, consist of studying a gravity dam monolith using, first, the gravity method (GM), second, the finite element (FE) method (FEM) with a simplified horizontal planar dam–rock interface, and, third, the FEM with a detailed irregular geometry of the dam–rock interface. In the first two steps, the simplification of the rock foundation geometry is paired with the implementation of apparent cohesion and friction angle into the models. These apparent parameters are evaluated based on nonlinear shear strength criteria combined with an interface roughness coefficient (IRC) introduced to characterize the roughness of a dam–rock joint extending along the whole dam footprint. This coefficient is approximated herein numerically based on FE models. The inputs and steps of the progressive approach are illustrated through several examples of typical dam–rock systems and rock profiles based on bathymetric and LiDAR surveys. The results mainly show that the effects of rock foundation roughness on dam sliding stability can be efficiently represented with apparent cohesion and friction angles. The effectiveness of the simplified models coupled with the conservatism of the results they provide are likely to favor their adoption by practicing engineers.