A Large-Scale Laboratory Experimental Study on the Behavior of Gravel-Concrete Interfaces Used in Dam Safety Evaluation

In soil-structure interaction studies, which include dam safety analyses, realistic modeling of the interface between concrete and coarse-grained soil is an important component. This includes, but is not limited to, the interaction between the concrete face slab with the neighboring cushion layer in concrete-faced rockfill dams (CFRDs). This paper focuses on data from an experimental program that is investigating soil-structure interface behavior at a large laboratory scale with appropriate boundary conditions. Global measurements of force-displacement along with local observations were evaluated for three different surfaces in contact with crushed limestone. While many researchers have investigated concrete-sand and steel-gravel interfaces, there is limited data on concrete-gravel interfaces. Tests on these surfaces, including smooth concrete, rough concrete, and a waterproofing membrane, were performed under a range of normal pressures, and the coefficient of friction was characterized for each interface. Experiments revealed that shear strength increased proportionally with normal pressure and that a minimal increase in concrete roughness increased the interface friction coefficient by a factor of nearly 1.5. The results on the membrane-gravel interface varied between the smooth and rough surface measurements. The rolling of particles was the dominant behavior under the concrete block, and a heap clearly forms in front of the block, which could be the cause of damage to CFR dams that have been subjected to seismic loads.