Mechanisms and simulation methods for extrusion damage of concrete faces of high concrete-faced rockfill dams

One of the key safety problems of high concrete-faced rockfill dams (CFRD) is the extrusion damage of the concrete faces. Based on analyzing several examples of high CFRD projects, the common features of extrusion damage of concrete slabs are summarized. The rotary contact-based extrusion, consisting of rotary extrusion and translational extrusion caused by the deformation of dams, is considered as the mechanism of extrusion contact between rotary slabs and the essential reason of extrusion damage of concrete slabs. Three-dimensional finite element numerical software on the basis of nonlinear contact theory is developed to solve the multi-body contact problem in CFRD. The numerical results of a submodel show that both the rotary extrusion and translational extrusion can cause severe local stress concentration on the surface of concrete slabs along the vertical joints, and that the phenomenon, which both the observed and numerical compressive strains at the middle position of the slabs are far below the ultimate value when extrusion damage occurs, can be explained reasonably by the stress concentration factor.