Contribution of 3D Roughness Along Concrete-Rock Interface to the Sliding Stability of Concrete Gravity Dams

Current engineering practice in dam maintenance and safety evaluation generally neglects the contribution of three-dimensional (3D) roughness along a gravity dam's base to its sliding stability. This important question is addressed in this article through the development and stability analysis of nonlinear finite element (FE) models of dam-rock foundation systems. These models implement realistic large-scale 3D dam-rock joints based on topographic data extracted from existing dam sites. Detailed analyses of the stability response of the studied dam-rock interfaces are presented in terms of limit friction angles, sliding safety factors, aperture and interface roughness coefficients (IRC). The effects of 3D roughness on the distribution of apertures and shearing stresses are discussed. It is shown that the location of asperities within a dam-rock interface may greatly affect the sliding stability. It is also found that 3D roughness may significantly increase the shear strength of dam-rock joints and that bidimensional (2D) sliding stability analyses may over-estimate the shear strength of natural shear keys. However, the asperities along 3D dam-rock interfaces are found to increase the global shear strength in comparison to 2D stability analyses. Limitations of currently available roughness parameters and shear strength criteria are also discussed.